This is the upper 32 bits of the total-received-frames counter, incrementing whenever the LSB half wraps around, mirroring the same split-counter pattern used throughout this radio's Ethernet statistics objects. Without tracking this half, a polling interval that spans an LSB wraparound would produce a nonsensical drop in the apparent received-frame count. A capacity-planning script computing long-term throughput trends on this radio hop needs to reconstruct the full 64-bit received-frame count from this and gnEthStatisticRadioReceivedFramesLsb together to avoid a false dip in its charted data whenever the LSB rolls over.