This is the object's Rn — the Relative Name, i.e. just the last path segment that the slot endpoint contributes under its parent's Dn. For this chassis slot's endpoint for whatever blade currently occupies it, the Rn is the naming component (built from things like chassis id, slot id or port id) that distinguishes this specific row from its siblings under the same parent container in the tree. A typical Rn here looks like 'slot-6', which is appended to the parent chassis/blade Dn to form the full path.