No, you misunderstand. The retina screen has 4X the pixels. The app, if it doesn't know that it's running on a retina screen, scales itself for the non-retina display. So if the app is 320x480 pixels (non-retina), shown on a retina screen (640x960), there is leftover space. I ran into similar problems with this when making my first app, but it was only happening for images, not the entire view.This is wrong. Retina or not doesn't affect how much of the screen Cydia would take up. Retina adds more pixels.