what is the meaning of the output of the users list command
The structure of the output is as follows:


  UserInfo{id:name:flags}


Flags are basically bits of information describing the data model's level of access and/or permissions.

You can read some of the code comments on the flags defined in the UserInfo class here:

https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/content/pm/UserInfo.java