What is the 2-digit Duress Code in terminal-setup and how to configure it?

The '2-digit Duress Code' was used for when someone was under the threat to open the door,he/she can enter the pre-defined 2-digit duress code along with his/her password.

So the device will send out an email or SMS notification to the administrator under the [Alert Log] settings.See the attached files as an example.

Attachments:
duress_enable.jpg
alert_setting.jpg