When a metric is created, every threshold needs a default value. This is used later when the metric is updated with an actual value. The thresholds are stored along with the actual values so that the software can show what the goals were in the past.
One problem with remembering historical thresholds, however, is that if an administrator wants to retroactively change them, she would need to manually change the thresholds for every historical metric value.
There is now the ability to override historical thresholds when changing a metric’s default thresholds. This will dramatically reduce administration time.