This field records how much the counter for frame transmission errors recorded for this network interface increased during the most recent collection interval, rather than the lifetime cumulative total. For a network admin, this tracks failures on the send path specifically, so pairing it with the interface's CRC (receive-side) counter tells an admin whether a problem is local to this card's transmitter or is coming in from the far end. For example, 14 frame transmission errors 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.