This is the relative name — the leaf portion of the distinguished name — that distinguishes this history row from its siblings within the same parent object. It matters on an archived historical sample row of that same receive-counter set, kept purely for trending past intervals rather than showing the current live value because it is the short identifier UCS Manager uses internally to address one specific archived sample without repeating the whole DN path. An rn like rx-stats-hist-21 on the endpoint this history row belongs to is what appears appended to a fixed parent path to form that row's full DN.