This is the Relative Name (Rn) of a Fibre Channel zone member entry representing a target (e.g. a storage array port) participating in a configured FC zone, the naming component that distinguishes this instance from its sibling ZoneTargetMember objects under the same parent in the UCS tree. Admins rarely read the Rn directly, but UCSM uses it to build the full Dn path, so it matters when correlating which parent object a given ZoneTargetMember instance belongs to. For instance, if two ZoneTargetMember objects sit under the same parent container, their Rn values are what tell UCSM (and any script parsing the Dn) apart which one is which.