Google Play Services Plugin Save/Load

I´m using official plugin:

https://github.com/playgameservices/play-games-plugin-for-unity

I have this code for saving and loading:

     System.Action<bool> mAuthCallback;
     
     GameData slot0;
     
     bool mSaving;
     private Texture2D mScreenImage;
     
     // Use this for initialization
     void Start () {
         
         slot0 = new GameData("New game");
         mAuthCallback = (bool success) => {
             
             if (success) {
                 Debug.Log("Authentication was successful!");
                 slot0.State = "Click load or save";
             }
             else {
                 Debug.LogWarning("Authentication failed!");
             }
             
         };
         
         
         PlayGamesClientConfiguration config = new PlayGamesClientConfiguration.Builder()
             .EnableSavedGames()
                 .Build();
         PlayGamesPlatform.InitializeInstance(config);
         
         // Activate the Play Games platform. This will make it the default
         // implementation of Social.Active
         PlayGamesPlatform.Activate();
         
         // enable debug logs (note: we do this because this is a sample; on your production
         // app, you probably don't want this turned on by default, as it will fill the user's
         // logs with debug info).
         PlayGamesPlatform.DebugLogEnabled = true;
         
         //Login explicitly for this sample, usually this would be silent
         PlayGamesPlatform.Instance.Authenticate(mAuthCallback, false);
         
         
     }
     
     public void CaptureScreenshot() {
         mScreenImage = new Texture2D(Screen.width, Screen.height);
         mScreenImage.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
         mScreenImage.Apply();
     }
 
     // Save Button
 
     public void SaveButton () 
     {
         int idx = slot0.Data.IndexOf("_");
         if (idx > 0) {
             int val = Convert.ToInt32(slot0.Data.Substring(idx+1));
             val++;
             slot0.Data = "Save_" + val;
         }
         else {
             slot0.Data = "Save_0";
         }
         mSaving = true;
         CaptureScreenshot();
         ((PlayGamesPlatform)Social.Active).SavedGame.ShowSelectSavedGameUI("Save game progress",
                                                                            4,true,true,SavedGameSelected);
     }
 
     // Load Button
 
     public void LoadButton () 
     {
         mSaving = false;
         ((PlayGamesPlatform)Social.Active).SavedGame.ShowSelectSavedGameUI("Select game to load",
                                                                            4,false,false,SavedGameSelected);
     }
     
     
     public void SavedGameSelected(SelectUIStatus status, ISavedGameMetadata game) {
         
         if (status == SelectUIStatus.SavedGameSelected) {
             string filename = game.Filename;
             Debug.Log("opening saved game:  " + game);
             if(mSaving && (filename == null || filename.Length == 0)) {
                 filename = "save" + DateTime.Now.ToBinary();
             }
             if (mSaving) {
                 slot0.State = "Saving to " + filename;
             }
             else {
                 slot0.State = "Loading from " + filename;
             }
             //open the data.
             ((PlayGamesPlatform)Social.Active).SavedGame.OpenWithAutomaticConflictResolution(filename,
                                                                                              DataSource.ReadCacheOrNetwork,
                                                                                              ConflictResolutionStrategy.UseLongestPlaytime,
                                                                                              SavedGameOpened);
         } else {
             Debug.LogWarning("Error selecting save game: " + status);
         }
         
     }
     
     public void SavedGameOpened(SavedGameRequestStatus status, ISavedGameMetadata game) {
         if(status == SavedGameRequestStatus.Success) {
             if( mSaving) {
                 slot0.State = "Opened, now writing";
                 byte[] pngData = (mScreenImage!=null) ?mScreenImage.EncodeToPNG():null;
                 Debug.Log("Saving to " + game);
                 byte[] data = slot0.ToBytes();
                 TimeSpan playedTime = slot0.TotalPlayingTime;
                 SavedGameMetadataUpdate.Builder builder =  new 
                     SavedGameMetadataUpdate.Builder()
                         .WithUpdatedPlayedTime(playedTime)
                         .WithUpdatedDescription("Saved Game at " + DateTime.Now);
                 
                 if (pngData != null) {
                     Debug.Log("Save image of len " + pngData.Length);
                     builder = builder.WithUpdatedPngCoverImage(pngData);
                 }
                 else {
                     Debug.Log ("No image avail");
                 }
                 SavedGameMetadataUpdate updatedMetadata  = builder.Build();
                 ((PlayGamesPlatform)Social.Active).SavedGame.CommitUpdate(game,updatedMetadata,data,SavedGameWritten);
             } else {
                 slot0.State = "Opened, reading...";
                 ((PlayGamesPlatform)Social.Active).SavedGame.ReadBinaryData(game,SavedGameLoaded);
             }
         } else {
             Debug.LogWarning("Error opening game: " + status);
         }
     }
     
     public void SavedGameLoaded(SavedGameRequestStatus status, byte[] data) {
         if (status == SavedGameRequestStatus.Success) {
             Debug.Log("SaveGameLoaded, success=" + status);
             slot0 = GameData.FromBytes(data);
         } else {
             Debug.LogWarning("Error reading game: " + status);
         }
     }
     
     
     public void SavedGameWritten(SavedGameRequestStatus status, ISavedGameMetadata game) {
         if(status == SavedGameRequestStatus.Success) {
             Debug.Log ("Game " + game.Description + " written");
             slot0.State = "Saved!";
         } else {
             Debug.LogWarning("Error saving game: " + status);
         }
     }
     
     
     public class GameData  {
         
         private TimeSpan mPlayingTime;
         private DateTime mLoadedTime;
         string mData;
         string mState;
         
         static readonly string HEADER = "GDv1";
         
         public GameData(string data) {
             
             mData = data;
             mState = "Initialized, modified";
             mPlayingTime = new TimeSpan();
             mLoadedTime = DateTime.Now;
             
         }
         
         public TimeSpan TotalPlayingTime {
             get {
                 TimeSpan delta = DateTime.Now.Subtract(mLoadedTime);
                 return mPlayingTime.Add(delta);
             }
         }
         
         public override string ToString () {
             string s = HEADER + ":" + mData;
             s += ":" + TotalPlayingTime.TotalMilliseconds;
             return s;
         }
         
         public byte[] ToBytes() {
             return System.Text.ASCIIEncoding.Default.GetBytes(ToString());
         }
         
         
         public static GameData FromBytes (byte[] bytes) {
             return FromString(System.Text.ASCIIEncoding.Default.GetString(bytes));
         }
         
         public static GameData FromString (string s) {
             GameData gd = new GameData("initializing from string");
             string[] p = s.Split(new char[] { ':' });
             if (!p[0].StartsWith(HEADER)) {
                 Debug.LogError("Failed to parse game data from: " + s);
                 return gd;
             }
             gd.mData = p[1];
             double val = Double.Parse(p[2]);
             gd.mPlayingTime = TimeSpan.FromMilliseconds(val>0f?val:0f);
             
             gd.mLoadedTime = DateTime.Now;
             gd.mState = "Loaded successfully";
             return gd;
         }
         
         public string Data {
             get {
                 return mData;
             }
             
             set {
                 mData = value;
                 mState += ", modified";
             }
             
         }
         
         public string State {
             get {
                 return mState;
             }
             
             set {
                 mState = value;
             }
         }
         
     }

With this I only save and load blank info, so nothing is saved, can anyone help me? I would like to know where I have to put the info that I want to be saved, for example, a float.

Thanks!