I didn't said that. English isn't my native language, so maybe i express my thoughts in a weird way, but what i mean was that it's usual for first year student to be 17 years old, not even 18. I didn't said that 19 isn't usual. It is usual too...
блэть на родном было бы проще... In short. Usual age for first year students is 17-19 years, where 17 and 19 more rare than 18. MC is 19 at the beginning of the year, so he is like in the end of that diapason (interval, range, whatever). I said that to point that Jill can't be more than 2 years older than him, because she's at the beginning of the third year, so she should be somewhere between 19 and 21.
That what i said.
Edit: Rereading what i wrote, i certainly use some wrong words even now, but i don't sure how to do it correctly. Sorry, it seems that all our conversation comes from my shitty English, because we basically said the same thing