Hello 13BooBoo13,
License number is not really relevant for free users, you can simply ignore it.
It is sometimes updated automatically. This automatic update of LN does not affect functionality of your AVG.
Thank you
My Free 2011 AVG did a big auto update today and when I looked at the History I noticed it had changed my AVG Licence number. Is this normal ? I am running Windows XP.
13BooBoo13

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic