This DisplayString reports the timestamp at which this bin's collection window closed, per its DESCRIPTION. Paired with StartTime, this confirms whether the elapsed time actually matches the row's Duration for this Basic Tx (forwarding) PM instance; a mismatch usually means the interval was cut short by a clock jump, reboot, or missed poll rather than running its full configured length. For example, an EndTime only six hours after StartTime instead of twenty-four tells you the device was likely reset partway through that period.