This Counter64 is the number of unicast packets received on this endpoint just since the previous poll. 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 a sudden drop in this delta while totalPacketsDelta stays flat would point to a broadcast/multicast flood displacing normal unicast traffic rather than a general slowdown. unicastPacketsDelta falling from 50,000 to 500 between polls on the endpoint this history row belongs to, with totalPacketsDelta unchanged, is the kind of signature an admin would use to spot an active broadcast storm.