Plesk backup restoration completes with the warning: Cannot set limit 'max_traffic_soft' value to '100': New value is less than the currently used amount of resources

Symptoms

• Restoration of a domain from a backup finishes with the warning below in Plesk:

  PLESK_WARN: WARNING: (Restore domain object 'example.com') Execution of /opt/psa/admin/plib/api-cli/domain_pref.php --update example.com -max_traffic_soft 100B -ignore-nonexistent-options failed with return code 1.
  Stderr is
  An error occurred while updating domain settings: Cannot set limit 'max_traffic_soft' value to '100': New value is less than the currently used amount of resources (87334116).

• The subscription example.com is customized in Plesk > Subscriptions > example.com > Customize and is not synced with any service plan;
• In Subscriptions > example.com > Customize > Resources tab > Overuse policy is set to Overuse is not allowed or Overuse of disk space and traffic is allowed.

Cause

The Notify when traffic usage reaches value is not defined for the affected subscription in Subscriptions > exampole.com > Customize in the Resources tab.
During the restoration of the backup, the old value of 100MB was not restored as it is less than the current one, which is in fact not defined at all.

Resolution

This warning can be safely ignored.
If required, adjust the Notify when traffic usage reaches value in Subscriptions > example.com > Customize > Resources tab after backup restoration.