The federation-info only lists 3,470 Calckey users and does not count the biggest Calckey server, which is calckey.social. And calckey.social has over 2,000 accounts. That's a pretty big server to miss.
And now let's consider fediverse.observer. They report a drop in Calckey users despite there being a big increase in sign-ups for May on calckey.social alone. Even more befuddling, they report 0 comments from Calckey. This is not possible. I'm seeing comments on Calckey daily.
https://fedidb.org reports an accurate count, which is that Calckey has over 9,000 accounts spread over 315 servers.
