That's calibre messing with your head
Seriously, calibre now uses amazon's "real page numbers" feature to add pseudo page numbers for your books. The pseudo page numbers don't correspond to any actual print editions. They're just estimations of pages in real books.
I like the pseudo page numbers because they're a little more human readable than locations, which are basically just the file size divided by 128. No doubt other prefer locations b/c they're more precise. But precision doesn't help if you can't freaking remember it.