This reports the received optical power level of this specific DWDM wavelength (optical channel), stored as a milli-scaled fixed-point number (PmInteger32Milli, i.e. the raw integer divided by 1000 gives dBm). Because this reading comes from the still-filling, live 15-minute bin for this wavelength/line, if this drifts down from where it was provisioned, it usually means this specific wavelength is losing power somewhere upstream -- a bad connector, a fiber cut, or an EDFA amplifier drifting out of gain -- well before the client signal actually drops. For example, a healthy 100G coherent wavelength typically reads around -12.500 dBm (stored internally as -12500); a reading that has slid to -22.000 dBm on this channel while neighboring channels stay flat points at a problem specific to this one wavelength, so far within this still-open 15-minute interval.