The Training Plan consists of separate Courses, Webinars, etc.
When you enroll learners in the Training Plan, you enroll learners in each of these courses. These courses can have the Due Date, and the Training plan may have it too.
When you create a report, you will see the Due Date for the Training Plan's Courses and the apart Training plan's Due Date. And you can see in the report situation with completed on-time Training Plan, and course overdue.