Please help. How much formula does your 3 month old eat in one feeding?

My mom says I can’t give more then 170ml which is annoying as heck because 180ml is 6oz why would I dump 10ml out? Anyways I don’t listen to her because it makes no sense to me. Right now I feed 6oz but he’s hungry still right after feeding he literally asks for more. What’s the most I can give him?