In June last year, this was the World Record for CCU / Online Players in a Roblox Game
Now it's a Friday @PlayAdoptMepic.twitter.com/DitRLuuoFM
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
You're making the mistake of tracking peak to drop, but you aren't accounting for the 200,000 players who joined and played within the 50 minutes it took to hit peak. More people join than leave = number goes up. More people leave than join = number goes down. Maths!
If you have other questions I'd be happy to explain. It can be hard to imagine, but players login/logout at the same time, so the number changing is just an indicator of login versus logout. Some people play for a few mins, some for an hour, but most somewhere in the middle
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.