Maybe it's the same as the previous verdicts?
Based from the combined replies from the two threads, it looks like an issue with accounts logged-in to multiple instances (eg. Bots).
Just read those topics for more info, there's no conclusion though.
Thats right. If you open 5 tabs of BTT, your online time will increase in 5x. Maybe there users are scraping the forum or simple trying to increase their online number for some reason. There are a few BTT copy capts that have pretty much all posts after a few minutes/hours so I bet on the first.