I feel like we always get taught how to use the first 10 numbers with counters, and above that we are just left to guess whether we have to use the same words but with other numbers before, or just use it “normally”…
Let me explain: for example, 1 person is ひとり, right? - but 31 people is さんじゅういちにん and notさんじゅうひとり. On the other hand, because four days is よっか, 24 days becomes にじゅうよっか and not にじゅうよんにち.
How are we supposed to know which way around is it for all numbers and all counters?
Do you know of any page detailing this?