How do I know when to change teats?

[Cemkg123]

My LO was breastfed up until 6.5 weeks when I switched to formula. She will be 13 weeks on Monday.
I have been using Dr. Brown's bottles with the first teat (slow flow). How do I know when to change her to number 2/medium flow?
Currently her feeding pattern seems to be during the day every 2-3 hours she will take about 3oz sometimes 4 but not too often. She goes to bed about 7pm and then wakes up at 2am and then about 5am then 6:30am. Is this normal? On the formula box it says her age should be taking 5oz 5 times a day? She has between 7-10 bottles a day.
Should I change to medium flow, will this help her take more? She fusses sometimes but i think its because she wants to suck on something but won't take a dummy. I've not seen my health visitor since my LO was 6 weeks so not been able to discuss it with her.

I’d pretty much ignore the guidelines on the carton, they are just that, guidelines and all babies differ. I think you are doing exactly the right thing by feeding on demand. Having said that, I would try her with the next stage teats, just because yiu say she sometimes fusses. You can always swap back for a bit if she doesn’t like it

If she starts sucking so hard that the teat starts to collapse, then move up to faster flow.

My baby is 9 weeks old and we change the teats to number 2 only few days ago. She was sucking so hard so we decided its the time now.
About the feeding- she has 7 bottles in 24 hours, but only one at night at 4am