Yeah you're right, just noticed it. I don't think it is very important but good that you reporteeit/mentioned it here. Maybe it has to do something with invisible members, online members that arent viewing the forums etc. But not sure , maybe it is a glitch indeed, we'll see
I was assuming there might be a lot of "invisible" members, but that doesn't explain much either since all that means is that their name doesn't appear on the "Active Users" list. So it may be a minor glitch.
Oh yeah, I forgot about this. The large number of members are probably due to the members who are online but are probably reading the manga/watching the anime/viewing Naruto info on the main page.