There are at least two ways to verify the status of the backup in ITA.
1. Verify via server Webmin
The Status page in Webmin may display the status of the latest backup.
2. Check the backup location
The default location is /data/backup.
In the backup directory, there are two set files for each scheduled backup. One is the backup file itself with the file format ".tar.gz". The other has the file format ".completed" to notify you that the backup was completed.