Keep in mind that because there are no official JLPT lists for vocab/kanji/grammar, it's always better to study a bit more than the expected minimum. For kanji that means going into N4.
PS: JLPT lists are pretty much all the same, the only thing that changes between different sources seems to be where the line is drawn between levels. Anything that's "missing" from N5 will show up in early N4.
I heard that 100 kanji or something needs to be memorised to pass the jlpt but renshuu only covers shy of 90 out of 100 (was it 86)
will the rest be mixed into the renshuu n4 schedules
A couple things:
There's an official list set by the education department.
The JLPT test is its own thing.
What I mean is that the education department already has an outline for the N levels. This is what is taught and is the standard in places like Renshuu. The picture set here is that N5 is 80 kanji.
So if there's some source somewhere talking about you having to learn 6 to 20 kanji more, that is not really maximizing your chances of passing N5, obviously. N4 contains 168 kanji! You would not know enough, and the reason they're saying you need to know more kanji is only because sometimes the JLPT might throw you curveballs. In that case, if you learned a handful more, it's not really gonna be enough for the off chance it tests you on something you don't yet know. Eeek! That's bare minimum, and so just not enough. Better to have covered your base level, then all of the stuff ahead of that. And I do mean all, if you want to be truly prepared. Makes sense, right?
Going beyond that, the overall landscape here is that the JLPT itself is business Japanese. Fairly common stuff, but it isn't exactly native. What does more than the JLPT is the kentei test. For its kanji tests, the average native speaker doesn't go beyond level 3, I think. If you pass that, you're safe.
