This read-only CounterBasedGauge64 reports the value at the end of the sampling interval, or the amount of change during that interval, for the interface's instance of the variable selected by interfaceTopNObjectVariable, but only when that variable points to a 64-bit counter -- it reads zero for all other cases. Admins use this alongside interfaceTopNValue to get accurate ranked figures for high-capacity counters like ifHCInOctets that overflow a 32-bit gauge. For example, on a 10 Gbps interface being ranked by ifHCOutOctets, this object would carry the actual octet count since a 32-bit gauge would wrap too quickly to be useful.