Newborn feeding

Our son is a week old and is formula fed. We were given a guideline from the hospital the most babies eat 2-3 oz every 3-4 hours. We took him to his pediatrician and he is measuring great and everything looks good! My question is he seems to want to eat about 2.5 oz every hour and a half for certain periods of the day then he will have a long nap and have to be woken up at the 3 hour mark. Does this seem normal? I know they say feed on demand but I’m worried to either over or under feed him! First time mom btw!