Depends on how it’s done. I mean (absurdly) you could ‘make everyone under 95 di

Depends on how it’s done.
I mean (absurdly) you could ‘make everyone under 95 disappear’, so to speak and then it’s just an ongoing question of limiting reproduction.
If you do it as I recommend, then at most six generations.
If you want less social disruption, then twice that.