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 is the still-open, currently-accumulating interval, its value is only a partial count until the bin's Duration elapses and it rolls into history -- polling it twice a few minutes apart is the fastest way to catch a fault building up in near real time. 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.