Useless Fact of the Day

From Raymond Chen, here's the answer to: What's the row of numbers on the copyright page of books?

(It should be noted that it seems like the use of that row of numbers is getting inconsistent. The O'Reilly books I checked didn't have that strip. Nor did the Subterranean Press books I just got. My copy of Ionian Mission, though, did, as did my copy of Seven Habits of Highly Effective People. I'm probably not going to check further.)