In the Time pop-up, accessed from Routine and Temporary Schedule pages, individual
activities can be assigned in either of two columns:
Default activity column: The activities in this column are used by default and it must be completely filled with individual activities from 00:00 to 23:59.
Over-ride activity column: Activities in this column override activities in the Default column. If there are no override activities this column should be left empty.
For example, you can create an In the office activity in the Default activity column and an override activity such as I'm at lunch or a I'm in a meeting activity in the Override column that overlaps the Default column activities.
This means that you can add or delete activities in the Override column without disrupting the activities in the Default column. This feature would make it easy for a PA, first thing in the morning, to set up several meetings that would take place later in the day using a single I'm in a meeting activity.