When the baby is fed formula it usually takes around 3 to 4 hours for the baby to digest around 4 to 6 ounces of the formula.
Sometimes they might digest the formula sooner and need more feedings and if they're hungry the baby will certainly let you know by crying until you feed them.
Babies will need around 4 to 5 bottles of formula fed to them per day so as long as you're feeding the baby between 4 to 5 bottles of formula per day the baby is usually getting enough formula to eat.
If the baby is a bit more hungry and needs an extra bottle of formula during the day it's perfectly okay.