Do you know why a bound print piece has to have a page count that is a multiple of 4?
Pages of a booklet are created by printing four pages (2 in the front and 2 in the back) on one sheet of paper and then folding that sheet in half. In the illustration you can see that each page is connected to 3 other pages. Because of the way a booklet is produced, you can’t have a random number of pages. It has to be a multiple of 4.