10-Digit Message in Adsense Payout via Western Union

Have you ever wondered what is the 10-digit number in the message of the recent Google Adsense payout via Western Union? I just claimed my March 2011 payout today and I noticed a message from Google Adsense containing a 10-digit number. I also asked my fellow Adsense publisher if their Western Union printout has a 10-digit message, and they said… YES!

I searched about it in Google and found nothing. I searched about it in the Adsense forums, and I found nothing.

Is this something? Or just nothing? If you know what it is, kindly share it in the comment field below.