If you look at a rack and you can see 3 items on each of 3 rows, there are 9 "facings". A gift card rack is likely to have, for example, 9 pegs for the cards to go onto. You could perhaps put 20 cards on a peg. The rack would still have 9 facings even if you filled it full of 180 cards. I don't do merchandising, but back 'in the day' when I was mystery shopping 40 years ago a lot of the jobs we did were to count the facings for specific products in stores because the corporations pay the stores for display space often by the facings involved.