20 year old, breast augmentation 620cc. Will they be bigger once they drop? (Photo)

Currently your breasts may be pressed flat and might have the appearance of looking bigger when they settle out. At 2 weeks you are only about 10 percent settled, shaped, softened, dropped and fluffed. "Drop and fluff" refers to the fact that as the skin stretches and the muscles relax, the implants move down and out slowly – about 1 percent a day. It’ll be about six weeks before they even begin to settle down, but they’ll be close to 80 percent settled and softened at three months. Watching their progress is like watching your hair grow. You don’t see a difference in your hair growth daily, but all of a sudden you need a haircut. 
Be patient after surgery. Give yourself a few months before making a judgment about your surgical results. You won't know the outcome until then. 
Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author

Thank you for your question. It is not uncommon to have swelling. Breasts may not heal at the same rate, causing one breast to appear different than the other. It can take up to 12 weeks for the implants to settle and you to see the final result. Follow up with your board certified surgeon to address your concern. Good luck!