Oh, I named it poorly.
It should be a constraints that avoids a short rest interval between two consecutive days. My school has classes in the morning, afternoon and night (different student sets, of course).
Some teachers have to work with some of the morning and night student sets. That constraint would prevent a teacher from teaching the last classes of a day and the first classes of the following day.
By law, every employee must have a minimum rest interval of 11 hours. At my school, it means "3 hours"/slots.