Enrolment does not guess a site. Until the machine has a group, Fleet pins it under Onboarding so it is not lost in the list.
Press Fleet. Onboarding is open at the top whenever a machine has no group. The row says no group yet, and set group opens the actions tab on that machine. Once it has a tag, it leaves this section and sits under that site. Name a machine and set its groups is that edit. Run scripts when a machine first connects is the separate list of commands for a new Windows server or PC.
A group is a path such as site/Melbourne. Picking one is Put a machine in a site. An alert rule or a roll-out on site/Melbourne covers everything under it. Scripts that should run the first time a machine of that type connects are a separate setup.