This counts Errored Blocks on this SONET/SDH port: the number of error-detected blocks (at whatever block granularity applies to this signal's rate) recorded during the bin, per the MIB's description. EB is the block-based error tally that feeds the G.826-style performance parameters for this port -- because it counts blocks rather than seconds, it can distinguish a bin with a few, heavily-corrupted seconds from one with light errors smeared across many seconds, which plain ES on the same bin cannot; this particular bin is a live counter that keeps accumulating until it is explicitly cleared rather than rolling over on a fixed schedule, so a large value mostly reflects how long it has been since the last clear. An EB count of 384 for this bin, spread across relatively few ES for the same interval, would suggest a small number of seconds carried a disproportionate share of the errors on this port.