stage size is not the same in smartphone

I have my stage set to 320x416 and when I look at the animation on an iPhone the width and height are large then the stage that I set. I have the ability to scroll left, right, up and down. This might be a zoom issue but I don't thinks. here is the URL mua ban nha dat

For example if you rotate the iPhone the start screen should go back to center.

Any ideas?