This Counter64, in bytes, tracks the total number of bytes the GSM modem itself has transmitted across all calls, distinct from bytes transmitted through the router's logical interface. An admin uses this modem-reported figure, the GSM counterpart to the CDMA total-transmitted counter, to track actual over-the-air usage for capacity planning or comparison against a carrier data plan. For example, comparing this counter's growth rate against a known monthly data allowance helps the admin project whether a GSM-connected site will exceed its plan before the billing cycle ends.