Auto-Delete Users is a new automated facility for deleting users who haven't logged into the system for a while. This will significantly reduce the storage costs for your apps.
To set up this feature for your app, go to Design | Core App Info | Auto-Delete Users page on brainCould portal.

Check the [Enable auto-delete for dormant users] checkbox inside the dormant users statistic infobox.

Under Setting section, the number of days is allowed to be modified, which could set between 150 - 1000.
Click button [Export Dormant Users] to generate an example export with some users that would be deleted by the current settings.

Exceptions
The Exceptions setting is used for preserving users who satisfy the setting conditions from being deleted. Currently, there are following conditions you can set from portal:

Email Notifications
This feature is used to send emails notification to the users prior to a certain setting deletion days. It requires a SendGrid template.

Archive Settings
Finally, you can choose to archive an export of the user's data (for a period of time) when they are deleted.
As a bonus, enabling this setting also archives an export of a user's data when they are deleted via the Portal, or via the DeleteUser() call on PlayerState