Teachers can not teach more than 3 consecutive periods without counting Planning time

In case, you wish to limit consecutive periods for teachers to "max 3" in a row you can use this global or individual setting.
Naši učitelia nemôžu učiť viac než 6 hodín za sebou

However, if there are some lessons for subject (usually Planning time) which you wish to exclude from this count of 3, then you can use this advanced relation: