This field records how much the counter for FCoE frames that failed to be transmitted correctly out this interface changed during the specific collection interval this historical record captured — a frozen snapshot of that one interval's increase, not a live running total. For a network admin, this is the transmit-side counterpart to errorsRx, and a steady climb suggests an adapter or fabric-interconnect-side problem originating from this blade rather than from the far end. For example, 12 frames in the last interval on this specific FCoE path would already be worth a closer look, since this counter should normally sit at or near zero.