This counts how many times this specific fault condition has occurred, recurred, since it was first raised. A high occurrence count tells an admin this is a flapping/recurring condition rather than a one-time event, which usually points at a different root cause, such as an intermittent hardware fault or a link that keeps bouncing, than a fault that's only occurred once. An occurrence count of 15 on a link-down fault over a short period would strongly suggest a flapping physical link rather than one single outage event.