This OID counts, in events, how many symbol errors have been logged against the outbound (transmit) side of this 40 Gbps Ethernet (40GbE) interface. While symbol errors are more commonly a receive-side phenomenon, tracking this counter on the egress direction as well lets an admin confirm whether an error is being introduced locally on transmit versus arriving already corrupted from the far end when troubleshooting a bidirectional fault. For example, if only the outbound-side counter climbs on a 40GbE trunk aggregating several client services while the inbound counter stays flat, that pattern points suspicion at this device's own transmitter rather than at the incoming fiber.