???Question for Moms of multiples???

Hi if your baby is on Formula and only two months. How long does the can of formula last for baby? I sent my baby to my mother’s house on Thursday morning with a brand new can of milk “not open yet” and here it is Saturday morning and she says he has no more milk! I don’t understand cause he has never finished a can of milk in just three days! Do y’all think she over feed him? Or does that sound about right you y’all? He drinks 2oz and 4oz bottles…4oz during the day and 2oz when he wakes in the middle of the night and just needs a snack to fall back a sleep…I’m a ftm myself and just looking for a little insight