How does delayed arming and guest detection work?

Delayed arming is an option available from Settings > Alarm, only if auto-arming is enabled.

This feature uses a combination of sensor data to determine whether any guest has stayed at home, which will then prevent the auto-arming of the alarm. If all regular smart home users left the house, the smart auto-arming system will start. At this point, if delayed arming is enabled, the system will wait 5 minutes before auto-arming. During those five minutes, it will listen to motion and door sensors to determine whether or not someone stayed home.  

Two scenarios can then happen:

• The system detects motion within 5 min, it will not arm the alarm. Then it will send a notification to the regular users saying that the alarm was not automatically arm due to guests remaining at home. 
• The system doesn't detect motion within 5 min, it will auto-arm the alarm.