If an Alert threshold is changed manually, there is another process that is scanned by the system every few minutes. It updates the alert status based on any changes.

By manually triggering the alert, the event was picked up by the second process. We report alerts by their initial trigger date. When the limit changed, the system looked for this initial trigger date which was back in November.  The graph in the notification is showing what is happening now. Once this alert is acknowledged the system will reset and treat this as an old alert, and the next trigger will be based on a time after today.