This read-only PerfCounter64 counts Severely Errored Seconds encountered by this SONET/SDH Section layer in the current bin, a lower protocol layer than the Line-level counters covered elsewhere in this table. It gives an administrator visibility into severe error bursts detected specifically at the section layer, which can indicate framing or regenerator-level issues distinct from line-layer problems. For example, a rise isolated to ocnStmStatsSectionSESs, with line-layer counters staying clean, would point to a section-layer issue such as a regenerator between the two line terminals.