Menu Building - Cannot implicity convert type float to int

Back again with a new noobie question.

So I'm building this main menu Rust style and I found a quality slider code for my options menu. Totally overjoyed I copy pasted it in my code to find the error stated below. If someone could point out the error and explain WHY this keeps happening you will probably never see this question again! Thank you in advance! Code btw is in C#

Error

 Assets/Scripts/mainMenuSliderScaleable.cs(68,49): error CS0266: Cannot implicitly convert type `float' to `int'. An explicit conversion exists (are you missing a cast?)

Code using UnityEngine; using System.Collections;

 public class mainMenuSliderScaleable : MonoBehaviour
 {
         //resolution settings
         public float originalWidth = 1024.0f;
         public float originalHeight = 768.0f;
         private Vector3 scale;
         //scrollbar settings
         public Vector2 scrollPosition;
         //menu settings
         public bool showOptions = false;
         public bool showCredits = false;
         public Texture2D MyTexture;
         //video settings
         public int gameQuality = 0;
         //audio settings
         public float masterVolume = 100.0f;
         public float musicVolume = 100.0f;
         public float SFXVolume = 100.0f;
     
         void Update ()
         {
                 AudioListener.volume = musicVolume / 100.0f;
         }
     
         void OnGUI ()
         {
                 scale.x = Screen.width / originalWidth;
                 scale.y = Screen.height / originalHeight;
                 scale.z = 1;
                 var svMat = GUI.matrix;
                 GUI.matrix = Matrix4x4.TRS (Vector3.zero, Quaternion.identity, scale);
                 //GUI.Box (new Rect (0, 0, Screen.width, Screen.height));
         
                 GUILayout.BeginArea (new Rect (20, Screen.height / 2 - 50, 200, 100));
                 GUILayout.BeginVertical ();
         
                 if (GUILayout.Button ("Start Game")) {
                         Application.LoadLevel (4);
                 }
                 if (GUILayout.Button ("Options")) {
                         showOptions = true;
                         showCredits = false;
                 }
                 if (GUILayout.Button ("Credits")) {
                         showCredits = true;
                         showOptions = false;
                 }
                 if (GUILayout.Button ("Quit Game")) {
                         Application.Quit ();
                 }
         
                 GUILayout.EndVertical ();
                 GUILayout.EndArea ();
         
                 if (showOptions == true) {
                         GUILayout.BeginArea (new Rect (300, 50, 600, 800));
                         //scrollbar
                         scrollPosition = GUILayout.BeginScrollView (scrollPosition, GUILayout.Width (600), GUILayout.Height (600));
                         //video
                         //quality
                         GUILayout.Label ("Video Settings", GUILayout.Width (100));
                         GUILayout.BeginHorizontal ();
                         GUILayout.Label ("Quality", GUILayout.Width (100));
                         GUILayout.BeginVertical ();
                         gameQuality = GUILayout.HorizontalSlider (gameQuality, 0, 5,GUILayout.Width(150), GUILayout.Height(35));
                         QualitySettings.SetQualityLevel (gameQuality);
 
                         GUILayout.EndVertical ();
                         GUILayout.EndHorizontal ();
                         //resolution
                         GUILayout.Label ("", GUILayout.Width (100));
                         //800x600
                         //1024x768
                         //1366x768
                         //1920x1080
                         //audio
                         GUILayout.Label ("Audio Settings", GUILayout.Width (100));
                         GUILayout.Label ("Master Volume", GUILayout.Width (100));
                         masterVolume = GUILayout.HorizontalSlider (masterVolume, 0.0f, 100.0f);
                         GUILayout.Label ("Music Volume", GUILayout.Width (100));
                         musicVolume = GUILayout.HorizontalSlider (musicVolume, 0.0f, 100.0f);
                         GUILayout.Label ("Effects Volume", GUILayout.Width (100));
                         SFXVolume = GUILayout.HorizontalSlider (SFXVolume, 0.0f, 100.0f);
                         //controller
                         GUILayout.Label ("Control Controls", GUILayout.Width (100));
                         GUILayout.Label ("Move Controls", GUILayout.Width (100));
                         GUILayout.Label ("Look Controls", GUILayout.Width (100));
                         GUILayout.Label ("Interaction Controls", GUILayout.Width (100));
             
                         GUILayout.EndScrollView ();
                         GUILayout.EndArea ();
 
                         GUI.matrix = svMat;
                 }
         }
 }