When people say there’s been an “𝑥 fold increase in such and such.” They mean such and such is 𝑥 times as big.
If you get something that actually folds like a sheet of paper, the amount of layers doubles each time. One fold = twice as many layers. Two folds = four times as many layers…
It is possible to fold a sheet of paper into thirds and get three layers…
But that would be two folds, and arguably two layers if the area of the middle section is bigger than the outer sections added together.
But you can fold the corners of a piece of paper, like dog earing the page of a book to make a quick bookmark, and unfolding that is very far from doubling the apparent, top down surface area.
There are many ways of folding things that are not the very specific ‘fold in half’ or bifolding that you are envisioning.
Ever made a paper airplane?
Origami?
Folded clothes?