That wouldn't explain where the 6112 users suddenly came from.
I noticed this as well. Within just a few hours a whole bunch of newer instances have suddenly shot up by several thousand users each. My guess is that people are using bots to take advantage of the sign-up bugs and are creating thousands of bot account to use in various annoying and nefarious ways in the near future.
Maybe. Instances full of lurkers ... it makes sense.
You can see the communities that users of that instance have subscribed to from the instance's main page: communities -> All.
In the case of parapheum, there's a few but not that many ... I'd expect more given a user base of ~7k.
If you go to fedidb (https://fedidb.org/software/lemmy ) they list the MAU (monthly active users) for each instance. Instances like parapheum only have like 1 or a few MAU. As I understand, to be an "active" user, one must post at least once. I presume this includes comments as well as full posts. If so, there should really be more than 1 MAU for ~7k users. So it's hard to tell.
I've checked the admins of a couple of these instances, and they seem to be real and have had interactions ... so maybe we should ask some of them what's up.