Divided cards are placed on too many positions in class XY

This problem is closery related to problem Class XY contains a window

Program automatically counts for every division how many positions can be fully occupied with its lessons.

There are some positions in the timetable where all students must have lesson, e.g. because of checking of windows in class's timetable, or because all students must start education at period 1. If you place cards from division on more such positions than can be fully occupied, program reports this error.