Why do book publishers countdown from 10 to 1 on the first page of all books?

I have noticed that on the first page of most books, publishers print a countdown from 10 to 1. It usually appears directly under the Library of Congress listing. For example look at page 2 of http://books.google.com/books?printsec=frontcover&id=BMgSvD39IzcC#v=onepage&q&f=false