Breastmilk feed per day

Hi guys, is 800+ to 900+ml of breastmilk per day enough for a 4 month old? I’ve noticed his intake has been stagnant since 2 months old. Currently 7.2kg and fully on EBM. Based on the calculation of 150ml x body weight, it doesn’t seem sufficient but I can’t see how I can further increase his intake!!