This reports the average total received optical power across the whole multiplexed line for the bin. Because this reading sits in the rolling window of completed 15-minute history bins for this wavelength/line, this aggregate average is what engineers watch to confirm the overall line power budget for this fiber span still matches the original design, independent of any single wavelength's behavior. For example, a total OTS average holding steady around -3.0 dBm for a fully loaded 80-channel line, versus a slow decline to -5.0 dBm over months, is the kind of line-aging signal this field is meant to surface, within that completed 15-minute window.