Flash builder weird screen resizing issue

I’m new to Flash builder and I’m having this weird screen resizing issue.

I’m setting up my .swf of dimenions…

 
[SWF(width="760", height="600", frameRate="32", backgroundColor="#000000")]
 

and I’m using…

 
stage.scaleMode = StageScaleMode.NO_SCALE;

but for some reason, which I don’t get is that when I do no_scale, the .swf window resized to 760x620, and I have these 20 pixels at the top, which are less than zero in Y, if I leave that line out, my graphics on the screen (isometric tiles) look distorted but the screen stays at 600 px in height.

any ideas what’s going on and how to keep it at 600 high and keep my graphics looking as they should?