Do you need to compress the standard stone wool when installing the fire damper close to the ceiling?

For rectangular dampers (CU-LT, CU2) the sealing between the damper and the slab can be done using stone wool boards (≥ 150 kg/m³) OR, if the space is equal to or less than 50 mm, using soft stone wool (≥ 40 kg/m³) compressed by at least 40%.