This field is the single highest per-interval delta value on the live, currently-updating stats object for physical-layer symbol errors — invalid line-code symbols the PHY detected on the wire — the worst burst seen across the retained collection history. This is the number to check after an alert fires, since it shows the worst single interval for symbol on this interface even if the current live value has already settled back down. For example, a recorded max of 38 symbol errors in one interval would flag the worst burst the interface has seen, useful for correlating against a specific outage window.