Feeding advice needed ASAP! First time cat owner!

How often are you feeding your cats and how much? We have an 8 month old kitten and recently adopted a 5 month old kitten for company. We’ve been giving them a whole pouch of wet food in the morning around 7:30am, half a pouch eat at around 3:30/4pm plus a handful of biscuits and then another whole pouch around 9/10pm. This is the schedule the lady from Cats Protection recommended to us. They also get a few dreamies a day and usually a few bits of plain cooked meat from whatever we have for dinner. Recently our 8 month old has been meowing at us a lot and digging at the dry food bag. Is she hungry or just being greedy? She’s never really been food motivated outside of dry food, which she loves and would only eat if we let her. They have Purina One Kitten wet and dry food as recommended by the vets as they came to us underweight.