You could think finding number 51 would be a piece of case

You could think finding number 51 would be a piece of case.
But in this case there has definitely been 'something else' in the designers mind. -Standard paper size and/or some readymade mechanics might be the good guesses..
Definitely this is as far from user oriented design you can go. Infact it almost feels like it is deliberate internal joke, which ended into production..

*update 17.4.2010*
Now compare to This one:

Flight patterns by Charlie McCarthy

I'm back from holidays. And in these cases I usually refer that first week after holidays, you should not work/think too hard to avoid injuries ;)
For htat reason an enjoyable video from Vimeo by Charlie McCarthy =)

flight patterns from Charlie McCarthy on Vimeo.