the meaning of "Include Days w/o Classes" ? (event offering)

Dear ALL

In the dialog creating business event(regular mode),

Schedule and Resource Reservation records are created by Schedule elements.

my question is how two check boxes in the region of Schedule and Resource Reservation work.

the check box(Include Non-working days) works with Factory calendar.

but i don't know how another check box(include Days w/o Classes) works.

what does "Days without classes" menas?

(I allready implemented SAP Note Nr. 1144972.)

Thanks

Regards