Page count.
The total number of interior pages always divides by two
 
Your page count is determined by the number of pages specified in your final PDF file. Your page count is always an even number and divisible by 2 (because every page has 2 sides). Standard MiniBük configurations increase in 8 page increments
from 8 to 48 pages for saddle stitching and 64 to 200 for perfect binding.