Auto it turns on to what you last had it set to when ON.
For example, turn it to ON, set it to 5, then set AUTO. That then tells it to go up to a maximum of 5 when it is triggered. Set to Auto and Temperature to 90f, it will turn on and slowly go up to 5 and stay on until under 90f.
The ALARMS can all be set to OFF, and AUTO then still functions just fine. I believe you hold down both keys (up and down) or the down arrow and it will go to OFF. Each is set separately in AUTO and ALARM. So 8 separate settings.