Runner visibility

I’ve setup a specific runner running on kubernetes using registration token on e.g. /groupname/project_foo, however

  • I’m able to see it also for /groupname/project_bar which is ok as it’s in the same group
  • I’m able to see it also for ‘/myusername/project_xyz’, why? Because I’ve created the runner?
  • My colleague can see it on /groupname/project_foo, why? Because he’s in the same group?

What are the rules for that runner being visibile in those projects? I haven’t found any reference of it