As long as he's gaining well I wouldn't worry. The rule of thumb is 2oz/lb/day.. so it depends how often he's eating, too.
Robbie is 9mo actual/6mo adjusted and still only takes 3oz breastmilk every 4 hours.And he actually eats less than that by mouth- I have to pump the rest in through a feeding tube. It's fortified to 24 cal w/prosobee but he's still not at the calorie intake he should. But he gains okay with that so his GI doc and pedi are happy. (Robbie has tummy problems so doesn't eat well. he having a hiatal hernia repaired and a G tube put in on Tuesday.)