Strange memory allocation by ActionScript3

programming flash
1

I use system.totalMemory to listen the memory-allocation
1)
I made a button and when clicked the button it would new a Shape and call its graphics method to draw vector lines and then addChild. But it is strange that when I click it first and the lines are drawn, the memory difference is 0. Then another more click, 0 too, and the third one will bring a “0.00390625M”(I divided the number by 1024*1024 to turn it to “M”) cost.

  1. I add a mc to a dynamic class, as:

     public function UploadDoc ()
 {
     init ();
 }
 
 private function init ():void
 {
     var button:CustomSimpleButton = new CustomSimpleButton();
     trace(System.totalMemory);
     button.aw1 = new MovieClip();
     trace(button.aw1);
     trace(System.totalMemory);
     delete button.aw1;
     trace(button.aw1);
     trace(System.totalMemory);
     addChild (button);
     button.addEventListener(MouseEvent.CLICK, doUpload);
 }

The output is
8724480
[object MovieClip]
8728576
undefined
8728576

Why after adding a MC, the memory is even more !?
and delete the MC did not make more…

It’s so strange that I don’t know what is wrong !
Anyone talks about it ? Thanks in advance!