Allowed items are included with your respective storage package. 6 items for the Economy Storage Package and 12 items for the Store-the-Dorm Storage Package. If your total items add up to more than the allowed number for your storage package, you can select "Additional Allowed Items" when purchasing your storage package. So if you're ordering the Economy Storage Package and you have 7 items, you would add 1 additional item ($20).
Below the Allowed Items is a listing of items that you can also store for extra cost such as Beds, Bikes, Couches and more.