I’m just guessing that it’s asking for surface area, since fabric doesn’t fully fill an object.
I kind of forgot about surface area so this isn’t going to be 100% accurate, but I believe that you multiply the base by the other numbers.
For example, you get the base of the side, 6 ft. , and you multiply it by the height, which gives 24. Then, you multiply it by 2, since there’s two sides.
Then you do 6x5 (30), and so on and so forth.
(I’m so sorry if I’m wrong, I haven’t really done area or surface area in a while lol)