See my Inventory entry for Wild Beastmaster. I have a total of three--two normal and one foil. I want two more normal (non-foil) copies, so I added the details for those two wishlist cards.

Now, when I view my inventory, I see a wishlist quantity of two on both line items: the entry for the non-foil cards, and the line for the foil cards. It makes it look like I am looking for a total of four.