Your content size is larger than your game view, so yeah there's bound to be some inconsistencies. 1 pixel according to NGUI (content size) is not the same as 1 pixel of your game view. If you make the game view match the UIRoot size, there won't be any gaps or padding. Anyway all of this is pointless anyway, assuming your target device is 2048x1536 (iPad?) -- as the downscaling to 960x640 is going to happen only in the editor.