This is the cumulative count of unicast (point-to-point) packets UCS Manager has recorded as received on this endpoint since the counter was last reset. It matters on the live receive-side counter set UCS Manager keeps for one Ethernet endpoint (a blade's vNIC adapter port, an I/O Module uplink, or a fabric-interconnect server port) inside a UCS domain because unicast volume is the actual application traffic component, so comparing it against totalPackets shows what fraction of received traffic is real payload versus broadcast/multicast overhead. If unicastPackets accounts for 95% of totalPackets on this interface, that link is carrying mostly normal application traffic rather than flood or discovery traffic.