Command to run before making changes to a server

When you goto Virtualmin> System Settings> Virtualmin Configuration> Actions upon server and user creation>

you will find a field “Command to run before making changes to a server” my question is about this field.

Is the command in the field fully completed prior to altering a domain (creation, alteration, or deletion) or is the command started and then altering the domain started prior to the command being finished?

If the command started and then altering the domain started prior to the command being finished is there a way to force the command to be finished prior to preceding?

Thanks AllanIT