I read this answer by Anony-Mousse to an other question related to density based clustering and how to potentially come up with an eps. It states, that if you want 90% of you points to be core points, you can use the 80% quantile of the 4-NN distances as your eps.
I just don't understand how the 90% core points exactly relate to the 80%-quantile of the 4-NN distances. Of course I get that they are related somehow, but I dont get the exact chain.
I've been thinking (and reading) about this for a while now and just can't come up with the answer, although it's probably pretty obvious?