Do we really need to follow the standard baby's formula milk chart or feed on demand?

Baby now is 1 month 1 week, 4.6kg as of 4 Dec. She can drink 110-120ml per feed every 2-2.5 hours, the longest is 3 hours. Is this normal? And if I gave breast milk of 40ml, top up formula milk of 70ml, sometimes she still not enough after finish the fm and cried, then I top up again 20ml and 20ml as she still not enough. Is this normal?#advicepls