Twitter changes the user interface almost constantly on its beta app - I suppose that's to be expected. The latest new feature in testing is a live counter for likes, retweets, and replies on each tweet. The counter appears to update roughly once a second.

The feature showed up for Artem on Twitter Beta 6.45.0-beta.599, but I am on the same version and don't have it, so perhaps it's a server-side test. You can grab that version from APKMirror if you want to check for yourself. Personally, I'm not really a fan - this seems visually distracting, and no doubt uses more cellular data (even if a small amount).