When an event has shifts, you may modify the displayed shift setting in the "event settings" so displayed shifts are either Open or Future.
Open = A user can still register to that shift
Future = The shift is in the future. Might be full, might not. Registration might be closed, might not.
As a individual looking at the event with shifts, they may override the above default and filter by the following:
All = Show all shifts - by default what an event uses
Open = As shared above.
Full = Shifts are full, Future or Past
Future = As shared above.
Closed = The shift could be in the future, but registration has closed for it
Over = Shifts in the past