alertThresholdType specifies whether a given alert entry's analog threshold triggers when the sensor value is lessThan or greaterThan the configured alertThreshold, and is irrelevant for alert entries tied to digital inputs. Admins set this depending on which direction of change is abnormal for the monitored sensor. For example, an admin monitoring for overheating would set alertThresholdType to greaterThan(1) so the alert fires when temperature rises above alertThreshold, while a low-humidity alert would use lessThan(0).