You send custom notifications to one particular reportee or a whole list of reportees within a category, in the Team Progress tab. For example, you might send a notification to all reportees in the Overdue category to remind them that they are now overdue.
You can notify:
An individual reportee in one of the categories
All reportees in the Overdue list
All reportees in the In Progress list
All reportees in the Completed list
All reportees in the Upcoming deadlines list.
...