This Gauge counts the number of times this line entered AIS (Alarm Indication Signal) alarm state during the current day interval, tracking discrete alarm occurrences rather than error-seconds. An admin cares because a high FC (failure count) tells them the line has been flapping in and out of AIS alarm repeatedly throughout the day, a pattern very different from one long continuous outage even if total downtime were similar. For example, an FC of 15 for the day indicates the line has been intermittently dropping into and recovering from AIS alarm fifteen separate times, pointing toward a flaky rather than fully dead connection.