I added a couple cards, then I added a couple foil versions of the same card and all it did was add to the existing listing and put the foil icon on it. It doesn't say how many of the cards are foil and how many are standard which can get very confusing.
My suggestion is to add a separate listing for the alternate versions of cards so they don't get mixed up along with the rest.
If you are viewing someone elses(or your own) listing you can click on the foil/promo/edition symbol on the right hand side of the name field. This will bring up the window listing the properties of each card.
That said, it would be nice if there was a multiplier next to the foil symbol if there are more than one foiled of the same card. It would allow for a quick visual reference on printed lists.