I took all the author user names that made a top level post (not a comment) in a month and then did a unique so each username was counted once.

I have no way of knowing if someone used three different accounts to make three different posts, and I know there are many who do this. But at the same time, I also know many users of Splinterlands don't post and only play the game, so without knowing how much of each, I just hope they balance out to be roughly the same. Either way, it's just an estimate based on the best viable metric.