This reports the Pre-FEC Bit Error Rate on this OTU signal -- the raw error rate on the line before Forward Error Correction cleans it up, stored in the atto-scaled PmCounter64Atto fixed-point format (roughly 1e-18 resolution). Because this reading comes from the still-filling, live 15-minute bin for this OTU signal, Pre-FEC BER is the truest measure of the actual optical/electrical signal quality on this link, since it is taken before FEC hides the problem, so this is the figure maintenance thresholds (e.g. 1e-5 or 1e-4) are typically written against. For example, a Pre-FEC BER around 1e-4 on this OTU signal is typical for a healthy coherent 100G link operating with margin, while a climb toward 1e-2 on the same signal would approach where even modern soft-decision FEC starts to struggle, so far within this still-open 15-minute interval.