I don't know how much food my 9mo baby should eat during the day in terms of serving sizes. I think I'm feeding her less.

Food introduction. The general recommendation for food introduction in infants is rice cereal at 4 -6 months, vegetables at 5 -6 months, fruits and fruit juices at 6 months, finger foods & meats at 9 months. A three meal two snack schedule is the usual goal, but adapting this schedule to your family's normal routine should be fine as long as your baby is comfortable and gaining weight appropriately.