Is 4 oz of formula every 2-2 1/2 hours normal?

I just don’t get it. I’ve read on web articles and on here how babies will go 3-4 hours on 4 oz of formula. She will only go 2 hours during the day and that’s including a possible short 15-30 minute nap. The only longer times between bottles are if we are driving around and running errands while she’s knocked out sleeping. I do get two 4 hour stretches at bedtime. FYI she is on Zantac for reflux 5ml 3x a day

Is there something I’m not doing right that’s causing her to be more hungry during the day? Should I be concerned? I thought the older baby gets = the more they drink in a sitting = longer between bottles?

Any advise is appreciated