This read-only Unsigned64 gives the average per-interval delta of deferred transmissions across all the sampling intervals collected so far for this interface's live, currently-active error-statistics record, smoothing out interval-to-interval noise. Admins trend this average over time on a given link to tell a persistent, low-grade problem from a one-off blip, since on the full-duplex fabric and adapter uplinks UCS uses this should stay essentially at zero, so any real growth here points at an unexpected half-duplex negotiation or a badly oversubscribed shared segment on this specific link. An average that creeps upward release over release on the same port, even while individual deltas look small, is the kind of slow drift that justifies scheduling a cable or optic replacement.