This counts High Correction Count Seconds at the OTU layer: seconds during which the FEC correction rate itself exceeded a defined threshold, per the MIB's description. HCCS is effectively an early-warning counter for this specific OTU section -- it flags the seconds where FEC had to work unusually hard even though it still succeeded, which is often the first measurable sign of eroding link margin (aging amplifier, rising loss) well before the fault becomes visible as SES or SEFS; as a 'total' bin it never rolls over on its own the way the 15-minute and 24-hour bins do -- it only resets on an explicit clear or a card reset, so a high count here just reflects long uptime, not necessarily an active problem. Seeing 4 high-correction-count seconds in this bin, especially if it recurs bin after bin, would prompt an admin to pull optical power and pre-FEC BER trends for this same port rather than wait for a hard alarm.