It's using this. @Vertex

Basically, I don't consider users that haven't be added to my database. My program runs 24/7/365 listening to events. The moment you are followed by someone that is highly reputable and, you get added to the database. So, from the 43M pubkeys reported in nostr.band, I only consider the 380k (supposedly real) ones.

The social graph is based on the Pagerank algorithm and the goodnpubs left are those who pass a minimum threshold rank