4 oz and 4 months

Hi. I have a 4 month old and we're currently giving him 4 oz to drink now he is gaining weight perfectly fine and we have an appointment on November 4 so I will ask his pediatrician, sometimes when we feed him he's still hungry and will cry and get fussy until we feed him more and sometimes he will eat cry and get fussy then we burp him and he's fine my mom and I are constantly arguing about how much he should eat I keep saying he had to eat 4 oz if we give him more were gonna overfeed him and she's saying it's not enough milk for him because he's still crying after we feed him even though sometimes all he need is a burp and he's fine I'm tired of arguing with her about it so how much milk should he be drinking?