This is inRangeDelta, the Counter64 companion to item 1 that reports only the in-range-error count from the most recent collection interval rather than the lifetime total. Because the cumulative inRange counter never resets on its own, this delta is what tells you whether the error condition on this interface is actively happening right now versus something that occurred long ago and has since stopped. For example, InRangeDelta reporting 40 during one 5-minute interval after several intervals of 0 signals a fault that just started on this specific link.