How many ounces (preemie)??

Hey! My daughter was born a month and a half early and she weighs 9 lbs now at almost 11 weeks. Does anyone else have a baby of the similar age? How many ounces do they eat per bottle now? How many times a day? My daughter drinks 2.5-3.5 ounces per bottle of 23 cal formula every three hours (sometimes four hours at night) and I feel like that’s such a small amount compared to other 2 month olds who are really chugging it at 5-7 ounces per bottle! Her pediatrician isn’t concerned but she’s below the 50th percentile for her adjusted chart and I’m just a little bothered!