Not to be the fly in the ointment, but you can’t really just add those up and expect that number to be accurate if we’re trying to look at unique users within the fediverse. If I had to hazard a guess, a not-so-insignificant chunk of those probably overlap (i.e. users who have made multiple accounts across several instances). I have made an account across lemmy.world, lemmy.ml, kbin and fedia just as backups in case one instance fails. I might be an extreme case having 4, but pretty sure it’s becoming increasingly common for people to have at least 2 accounts (1 on a different instance).