This Counter64, in bytes, tracks the total number of bytes the GSM modem itself has received across all calls, distinct from bytes received at the router's interface level. An admin uses this alongside the transmitted counter to build a complete picture of a GSM device's over-the-air data consumption for billing or capacity purposes. For example, a GSM router whose received-byte counter grows unexpectedly fast overnight might be pulling large unattended downloads that are eating into a metered data plan.