F.K.
My pediatrician told me that a breastfed baby should have twice his weight in ounces of breastmilk so if he's almost 12 and a half pounds then he should have 25 oz of breastmilk per day.
My sister is a pediatrician and she says to give the baby as much as he will drink and feed him until he refuses to eat anymore.
Personally, I think to just let him decide how much milk he wants. I pumped and bottle fed both my sons. I'm still pumping and bottle feeding my 9 month old. The odd thing is both my sons were 9 1/2 pounds at birth but my older son who drank much more milk, was much smaller. My younger son drinks much less mommy milk so I worried that he would be underweight but he actually is taller and weighs more than my older son so you never really know. I think the babies know how much milk they need. It's a mystery to us mommies:)