Every so often we throw in a box, star, octagon, or whatever into an illustration, then move it to the side and forget about its existence. Unfortunately, extra shapes outside of your artboard can cause an unnecessarily skewed image size when your file is rasterized or imported into a page layout program. When you’ve finished drawing make sure you zoom out and delete any extra shapes floating outside of your artboard.
You should also check your image closely to make sure you haven't left any hidden layers in your file, or forgotten any unnecessary shapes in the background of your composition. Please check your file in preview (also called "outline" or "keyline") view to ensure your illustration contains only the elements you want it to.
Unnecessary shapes and/or points hanging around on your pasteboard or in the background of your illustration will likely result in your submission being declined.