Formula oz

My daughter will be 8 months on the 30th she drinks about 4.5-5oz every 3 hours. I’m a little concerned, I thought by this age they were supposed to be drinking more. She’s getting solids twice a day. Her pediatrician doesn’t seem to be concerned about her only drinking 4.5-5oz but everywhere I see most babies are drinking 6-9oz she’s about 18-19 lbs she Also sleeps through the night and her bedtime is 8pm