The new rule is: "Offering multiple quantities of a reward is prohibited. Hardware and Product Design projects can only offer rewards in single quantities or a sensible set (some items only make sense as a pair or as a kit of several items, for instance). The development of new products can be especially complex for creators and offering multiple quantities feels premature, and can imply that products are shrink-wrapped and ready to ship."
It explicitly says that you can offer a reward of one of the item in question (or whatever the most useful set of them is). You cannot, however, have all of your reward levels be different quantities of the item.