As long as the baby is feeding well it shouldn't be a problem. Yes most of the time it will depend on the baby's weight = amount of milk intake. But remember that she is on FM and BM. A baby's stomach can't take in too much or it will lead to bloating and vomiting. As long as she is on demand, never miss her feeding time it should not be a problem too. Every baby is different. A guide is a guide. At the end of the day you make the adjustment. Some babies will be on demand, some babies will drag their feeding time despite you trying to feed them (they sleep a lot and don't drink much)