The number of orders per listing is only sorting per page, not for all pages. Here's the steps to reproduce the issue:
1) Go to Shop Manager and click on Stats
2) For the time frame, select "All Time"
3) scroll down to where it says "shoppers viewed your listings x amount of times" and select All Listings from the dropdown menu
4) Click on the header that says "Orders" so it sorts items with the most orders first.
5) Scroll down and click on pages 2 and 3. Notice the number of orders; it's sorting just for that page not all pages.
