Here goes, for those who don't know....

The number does stand for the distance around the chest. There are two schools of thought on that. If you go and have a bra fitted at the local Victoria's Secret, however, they will measure you all of the way around, from nipple to nipple (you are in your bra of course) to get that number. It's pretty much a personal choice and a comfort issue.

The letter size indicates the cup size, meaning how much boob you have. The sizes range from AA to H and over, depending on the boob size. There are tons of porn stars that have Fs and Hs, and I think anything over DDs have a hard time buying bras locally and have to go to specialty stores or buy online!

Hope this is helpful!