That’s the version of the Truenas Plex app and is determined by their developers. They make changes to their container from time to time and it tracked by the “app version.”
This is separate of the Plex Media Server version being deployed. If you’re on the stable train, they’re currently on PMS version 1.42.2.10156-f737b826c as can be seen here:
That is the current stable version, per:
There are newer beta versions, but you might want to stick with the stable track unless you’re willing to test for and report bugs/regressions.
