In the Coverage panel in Schedules, at the start and end of each cell are thin slivers of space that let you know about the times before and after demand for the day:
Role feature access: Schedules > Coverage Pane
Ideally, these slivers of space at the start and end of each day will remain blank, because there’s no demand at this time, and as such no one should be scheduled during this time. However, if an employee is scheduled during this time, the sliver will be shaded red (that is, overstaffed) to indicate that someone is scheduled too early or too late, as shown in the following example:
Managers can click this cell to open the day where the employee is scheduled too early, and can make the changes needed to the schedule to remove this red “overstaffing” shading from the Coverage panel.