DD is eating 15oz while I'm at work!!

ADL2010

I am wondering if this could be normal but my DD who is 5 months old is eating about 13-15oz of pumped milk during the day while I am at work.  Usually this is broken up over 3 bottles.

My son usually only ate about 10-12 at the same age so I am not sure if my dear daughter is being over fed or if she is just a little piggy chowing down on the bottle.  I know my DS drank from the First Year Breast Flow bottles which I know made him worker harder.  My dear daughter refused to eat from that bottle and is eating out of a nuk nipple slow flow level 0.

My only real concern is that I am only pumping about 12-13 oz while at work so what I am producing isn't necessarly keeping up with her eating demands.  I fortunatly have about a 3 day buffer built up but I am just wondering what other mommies are seeing as typical consumption during at 9 hour day for their 5-6 month olds.