How much to feed my daughters Betta?

I recently bought 2 betta for my daughter. She's too young to take care of them all the way but she does like to help feed. Well the store told us to feed them up to six pellets each depending on whether they'd eat it within 3 minutes. Im feeding them 5 pellets each at the moment & they gobble it up in NO time. I'm scared of over feeding them... should I give them another pellet? Also should i only feed them once a day or twice?