This is the cumulative CRC errors on received frames counter: counts Fibre Channel frames this port received whose cyclic-redundancy-check failed, meaning the bits were corrupted somewhere between the sender and this receiver. On one specific historical error-statistics snapshot for an FC port, this is the lifetime tally, so a rising count points at a degrading link (worn connector, bent fiber, failing SFP) rather than a software problem, since CRC checks happen in hardware below the frame-processing layer. For example, a healthy 16Gbps FC uplink sits at 0 for weeks, then jumps to 40 overnight when a technician reseats a patch cable without cleaning the ferrule.