media user and group automatically created, can't delete

[Prasanth]

I just freshly installed FreeNAS 11 U2 from the iso and imported my old pool into it. I was on corral prior to this and just wanted to update to the current 11 branch. Since there were so many changes I decided to start the setup from scratch.
As I went through to set it up plex,sonarr,radarr etc I tried to to create a media user and group only to find out they were already present. The problem is, I didn't create either one yet. They both have unusual Ids and I can't change or delete them! Attached is a screenshot of the user with its unusual UID.

Anyone know how to fix this?
Is this because I imported my old pool?

 

[Redcoat]

Those are defaults in FreeNAS - see here for more info.

 

[Prasanth]

Those are defaults in FreeNAS - see here for more info.

Thank you that explains a lot. So this media user and Group will also get added to the jails whenever one is created. Does it matter what type of jail?