This reports the average total received optical power across the whole multiplexed line for the bin. Because this reading comes from a closed, completed 24-hour history bin 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, across that completed 24-hour day.