Inconsistent, "snacky" eating

[u/iamchrysanthemum]

My baby is 3 months old and I still feel like I haven't gotten the hang of bottle feeding. Basically, I find it very hard to know if she is hungry, to predict when she'll be hungry, and how much she'll be hungry for.

For example, for her first bottle of the day after 9+ hours, I'll always propose 150ml but she'll often only take like 90ml. But then later in the day, when she's been fed consistently 120ml every couple of hours, she'll suddenly demand like 180ml and I have to go back and make more. Sometimes she'll go only 2 hours before screaming her head off for milk and sometimes she'll go several hours and then only lackadaisically take that bottle.

My doctor + the back of the formula box seems to suggest that by this age, babies should be pretty well-regulated to have X bottles of Y quantity per day, and I feel so far from that.

Is this normal? Part of me is telling myself that adults have varying appetites throughout the day so why should we expect babies to be robots? My concern is mostly (1) logistics—lots of making milk she doesn't eat and/or having to go back and make more (2) feeling bad that I'm maybe bad at reading her cues (3) my doctor is pushing pretty hard that I shouldn't let her "snack" and hold to at least 3 hours between bottles and push for 150ml per bottle.

[u/PermanentTrainDamage]

Feeding is individual, your baby can't read the formula box. If she wants 90ml for breakfast, make 90ml. Daily total matters more than bottle total, just like your daily calories matters more than how much you eat at each meal.