You have noticed that you have a large number of versions for a specific video file and you are asking yourself what is going on, why do I have 100 or 300+ versions?
Don't panic it means that you have used video player with thumbnail seek enabled.
If a player has thumbnail seek enabled, version generation happens when users scroll over the video players seek bar with the mouse and for every second of the video, we generate thumbnail.
If you don't want to generate these thumbnails in future disable seek preview in the player and we won't generate them.
If you are concerned it takes a lot of space, be aware that these thumbnails are only a few kb in size 2-3kb, and in total, they should not take more than 1-2mb.