EBF bottle feedings?

My baby is exclusively BF, he is 7weeks old. In the beginning I had an oversupply and stashed a ton of milk, I also Haaka everyday to add to stash. I rarely have a reason to use this milk because I am a SAHM currently. The only time I have used it is if I’ve drank or someone is babysitting him and he needs to be fed.

My question is... how do I know how much should be given? I store it in 4-4.5oz. Is it just assumed that is about how much they take? That is what I hear everyone say they store it in.