Look out for baby’s cue. This is what I personally did. If you think he still wants more after his usual feeding, make 30ml (first time), gauge how much to increase by his leftovers/when he spits up. However, I’d still recommend to increase 5~10 ml each time. And if he is on bm, don’t have to increase as frequently as fm. My LO was drinking 80~100ml (bm) from 3mo all the way till 8mo. Tried increasing but she won’t finish. As on now (15mo) she’s drinking 210ml.
TMC recommended multiple newborn weights with 150ml, dividing the no. of feeds per day. For example: 4.5 x 150 ÷ 8 = 84ml