This is the State of this SONET/SDH port bin, an enumerated value (PmBinState) whose exact label set isn't given in this excerpt, but per the MIB's description it reflects the bin's own status. Before trusting the Cvl/Esl/Sesl/Cvs/Ess/Sess values sitting in this same row at face value, an admin would check this state field first, since it's what would flag whether this port's measurement window was complete and valid rather than cut short by a reset or day-change; because this bin spans the whole current day and is still open, short error bursts get averaged into a slower-moving daily total -- useful for spotting a low-grade, chronic problem that the 15-minute bins would report as merely noisy. If this field for a given row came back indicating an incomplete or invalid state, an admin would discard the Sesl/Sess values sitting next to it in that row rather than read a run of zeros as a clean interval.