A good chunk of those could've made accounts but not stayed long. And how do they get those numbers? Because there were many people who did accounts in more than one instance.
Although I originally thought that AskLemmy was made as an equivalent to AskReddit, it's clearly different. On Reddit's it was limited to open-ended "thought-provoking" questions meant for discussion, whereas here it seems like anything goes. The purpose of this community seems to be much broader, that or it's just totally unmoderated lol. Not that that's necessarily a bad thing.
But maybe there should be another community for just the sorts of open-ended questions that we saw on Reddit