Resizing Sprites

I’m working on an app that allows the user to place images on the screen and move them around and resize them. These images are placed inside of a sprite that acts as a container for the images, which are in turn placed inside of another sprite. When I directly change the width/height properties of the image containers, the boxes don’t retain the correct values (whatever I set width and height to). For example, if I resize one of the sprites to 100x100, the box may actually be 90x90 and the Bitmap inside the box may be 80x80 (not a real-life example).

I vaguely remember reading something about the size of a displayobject relating to its container display object, but I don’t remember the details. I want to say this has something to do with scaleX and scaleY. Can someone shed some light on this resizing issue? Thanks…