he should eat as much as he wants, when he wants until he is full. babies dont come with a manual and they shouldnt eat a specific amount at specific times, theyre all different jsut tend to your babys needs and follow babes cues. my daughter (born 7lb 8ounces) had 2 ounces every 2-3 hours but i know a baby who had 4-5 ounces every 3-4 hours from birth like double what my daughter had, hes always been big though from birth and now is big at a year old aswell x