Well I don't know what the numbers stand for (well it's obvious that higher numbers means bigger breasts) but I do know that size is larger as you go through the alphabet. For example, Pamela Anderson (and most other stars in her...genre) have like 36C's or double d's, while anything from A to D is normal (yes, there is a Z cup, but I would NEVER want to see it!!).
For you girls, I want you to know that some guys REALLY care about breast size. I find this shallow and demeaning. There are also many guys (like me) who appreciate all "shapes and sizes", and it is the person that really counts.
So be proud with what you have! If you feel too small, some guys find small breasts attractive (not prepubescent small, that's perverted). I couldn't care less your size if we had a meaningful relationship (like trigger seems to have; lucky guy
EVERYONE is different, and EVERYONE is BEAUTIFUL!
SO BE HAPPY!!!!!