I've used a calculation to figure out feeding amounts. It's their weight x 2.5 then divide by how many feedings per day. That should give you the oz per feeding. Also look up pace feeding. It's really important for the baby to take their time to feed and not be chugging the whole bottle in a few min. I made that mistake with my son. At 2-3 months he's taking 6-7oz because we were just letting him chug.

some babies don't, but if he finishes that much I'd try a pacifier (he might just be wanting to suck) wait 15 minutes and then offer him another 2 oz. he might just not be realizing he's full