This setting is available on many screens including the dashboard, My team, opportunities, applications and event.
As this is a shared setting, if you select All in the dashboard, that will be the setting in My Team.
Changing it in the My Team listing will also change it in the dashboard the next time you go there.
My volunteers: All volunteers for whom you are named manager.
My team: All volunteers for whom you are a named manager and/or supervisor.
All volunteers: All volunteers for whom you are in the same team or above their team in the hierarchy, and/or are the named manager or supervisor.