Many surgeons use a very careful dissection technique in creating an implant pocket during breast augmentation, and the amount of swelling and bruising may actually be quite minimal for the patients lucky enough to have such careful surgery. Sometimes post-operative nausea, vomiting, or excessive activity can lead to increased bruising, swelling, or bleeding that can require re-operation, so even careful surgery needs good anesthesia, and compliant post-operative patient recovery in order to minimize these concerns.
Unfortunately, some breast augmentations surgeons (often those who are not fully-trained and American Board of Plastic Surgery-certified plastic surgeons) use blunt dissection technique or are less fastidious about control of bleeding vessels, and their patients often have significant and very visible swelling and bruising. I have seen many patients from other surgeons who feel that their breast size "went down by half" compared to the swelling they had immediately after surgery. My own patients hear this from some of their own friends who have surgery elsewhere and are concerned that they will lose size as time goes by.
Of course, implants don't change in size, but the tissues that cover and enclose these implants do soften, stretch, and allow implants to drop and settle into a final position. All the while, swelling in the surrounding tissues (sternal or cleavage region, flanks, back, ribcage and even abdomen) diminishes and reabsorbs during the healing process. The tightness and artificial height of the implanted breasts also decreases, and the breasts drop and actually project forward slightly more over time, achieving a more natural teardrop shape (when upright). Many patients perceive this as a slight size increase, not a decrease, unless they consider "high and tight" to be larger!
Ultimately, you should wait for 3-6 months to see how your breasts look with your new implants. Most patients are pleased, but there are still those who wish for larger implants and ask for re-operation. Your surgeon should have discussed these fees with you before your initial surgery. This is also why I generally recommend that patients choose slightly larger than their perceived "ideal" implant choice pre-operatively, as the single most common reason for re-operation is size increase, not any other complication or concern! Best wishes!