Personally, when I see "very large" busts, I expect to see something that would rival Tifa from Final Fantasy VII. That girl had a VERY large bust. So, I expect a "very large" to be Tifa - sized, while the "very large" now should be medium, and "very small" should be about the size of mosquito bites.

On an unrelated note, I believe that the dev team must think of us as perverts for comparing bust sizes on human-like females...