After AssetBundle.Unload(true) the memory is not clear.

 using UnityEngine;
 using System.Collections;
 
 public class Test2 : MonoBehaviour {
 
     void OnEnable () {
         for(int i = 0;i < 20;i++)
             Test1();
     }
     public void Test1 () {
         AssetBundle Temp;
         Temp = AssetBundle.LoadFromFile(Application.dataPath + "/AssetBundles/AssetBundles");
         Temp.Unload(true);
         Temp = null;
         Resources.UnloadUnusedAssets();
         System.GC.Collect();
     }
 }

link text I run this CS code. Why the memory of unity is increasing along. I want to know why it is unuse for System.GC.Collect();