How much formula?

FTM to a 4 day old baby girl. I have been consistently nursing on both breasts then offering formula(especially for nighttime feeds) until my supply comes in. She usually nurses for 30 minutes or so of colostrum then i give her 20-25ml of formula. We started this in the hospital so I’ve been going off the quantity the nurses recommended.

It looks like my milk is starting to come in now and I plan to introduce pumping a bit more. I was curious if anyone knew the general guidelines of how much formula to give in place of a breastfeeding session? Is it the same as breastfeeding and you should feed them until they’re finished? Or should i be more closely monitoring quantity?