This counts High Correction Count Seconds -- one-second intervals during the bin where the FEC correction rate on this OTU signal exceeded a defined high-water-mark threshold. Because this reading comes from the still-filling, live 15-minute bin for this OTU signal, HCCS is designed as an earlier warning than an outright FEC failure: it flags seconds where the correction engine is working unusually hard on this signal well before the link risks going uncorrectable. For example, an OTU signal that starts logging HCCS occasionally in a bin, even with zero uncorrected FEC blocks, is the kind of signal that justifies scheduling a proactive fiber or amplifier check before the link degrades further, so far within this still-open 15-minute interval.