My 535 cc UHP silicone implants look so small. Will they increase?

At only two days post operative you are extreamly early in the heaing process and your breasts with time will be under going a lot of changes. Be patient. Follow up with your surgeon as directed. 

You are very early in your healing phase, and need to give yourself time to heal and let the implants settle. The size you have is a large implant, and is the size you and your surgeon selected. Let your surgeon know how you are feeling, but be patient. You  may find that you love your new look once the breasts have healed.

I'm sorry to hear about the concerns you have after your procedure.
You should be aware that a significant percentage of patients at your stage of recovery will feel that they are too big or (more commonly) too small.I routinely ask my patients to wait at least 3-6 months before evaluating the end results of the breast augmentation surgery. This waiting time allows patients to (usually) physically and psychologically adapt to the new body image. Factors such as swelling, tissue contraction, skin redraping, implant shifting, "dropping and fluffing" etc. come into play.
From the psychological standpoint, patients undergo an “adaptation period" during which time they get used to the changes that the surgical procedure has brought about. Severe emotional swings can also occur after any type of surgical procedure.
Obviously, it is best for patients not to be making important decisions ( for example about the results of surgery and/or the need for additional surgery) while they are experiencing these emotional “ups and downs”.
In your case, I would suggest continued patience. Continue to follow-up with your plastic surgeon.Don't be surprised if/when you end up very pleased with the longer-term outcome of the procedure performed. Best wishes.