Number of students in class and groups

You can specify the number of students for every class and all groups in the dialog "Divisions" (use menu "Classes -> and select the Class).

Select Entire class and use "Edit" button. Then you can specify exact number of student for this class.

In a similar way you can also specify the size of each group in division. Just select the row with division and in the new dialog select "Number of students". Then just input numbers of students in every group.

See also:
Classroom capacities