Patients often get "hung up" on 25cc differences, and will even argue with their surgeon about 304cc vs. 325cc implants. Please realize that 21cc is a tablespoon and a teaspoon of volume! Over an entire breast you would never be able to tell the difference between either of these. If you are "too small" with the 304cc implants, trust me, you would have been "too small" with the 325cc implants. Likewise, if you would "topple over" with 325cc implants, 304cc would still make you equally top-heavy! Shame on your surgeon for using that example--304cc vs. 600cc, now there's a difference to argue about, and that difference is just over a cup size bigger!
I tell patients that it takes about 60cc difference in breast volume to even BEGIN to see a difference in size, and that 100cc is noticeable, but not a huge difference. It takes about 250cc to enlarge one cup size, and this has been borne out by thousands of breast implant patients in my practice over the past 24 years. (Apologies to those who suggest that 150cc equals one cup size--I just don't agree, but whatever scale each surgeon uses is OK so long as each of us is consistent with our own patient population.)
It sounds as if your surgeon had clear ideas about what he or she felt was appropriate for you--perhaps the swelling is actually around your new breasts, and your breast size really won't change very much. You may find with time that you actually are closer to your asked-for size than you think right now. Maybe not. But it's too early to ask for a size change now; you should wait at least 3 months; 6 months would be better! For more information about choosing size and this operation in general, read the link below, and the article "What is the Right Breast Implant Size for You?" on my About page on this site. Good luck!