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 specific bin belongs to the completed-interval history table, its value is frozen the moment the interval closes, so re-polling it later will return the same number -- useful for pinpointing exactly which past 15 minutes a problem occurred in. 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.