If your pit is 9 months old, short and stocky, and already weighs 63 pounds, I hate to break it to you but you do not have a pit bull.
More than likely, you have an American Bully. This is a newer “breed” of dog that has come onto the circuit that backyard breeders are trying to pass off as “big, blocky, and heavy pit bulls.” They aren’t. They are crosses of pits, American Bulldogs, and the English bulldog (to give it the stocky look). They can grow to weigh over 100lbs, males especially. I saw one come through the other day that was 130 pounds. Sweet as can be, but massive as all get out. That is not the way pit bulls are.
The weight of an average male APBT is between 35 to 60 pounds, and a female is 30-50 pounds. Those are the standards according to the UKC and reputable breeders. Of course, there are “pocket pitties” out there (tinier pit bulls that just have stunted growth) and larger pitties, but not like what you have!
Regardless, you will have a great dog (not to mention big)!