"UID -2" in btmdump output

Within the output of command "sudo sfltool dumpbtm", in addition to records for UID 0/501/502/..., at the top of the output, there are also records for "UID -2" listed.

========================
 Records for UID -2 : FFFFEEEE-DDDD-CCCC-BBBB-AAAAFFFFFFFE
========================

 ServiceManagement migrated: true
 SharedFileList migrated: false
 LaunchServices registered: false

 Items:

 #1:
                 UUID: FC60A3EA-E4B0-4D8C-BA07-1C6E2DF3AA52
                 Name: (null)
       Developer Name: (null)
                 Type: developer (0x20)
                Flags: [  ] (0)
          Disposition: [disabled, allowed, visible, not notified] (0x2)
           Identifier: Unknown Developer
                  URL: (null)
           Generation: 0
  Embedded Item Identifiers:
    #1: 16.com.microsoft.teams.TeamsUpdaterDaemon

But a uid with -2 should be invalid, and the guid "FFFFEEEE-DDDD-CCCC-BBBB-AAAAFFFFFFFE" followed looks also strange.