In moodlecode/backup/util/helper/backup_cron_helper.class.php
/** Course automated backup completed successfully */
const BACKUP_STATUS_OK = 1;
/** Course automated backup errored */
const BACKUP_STATUS_ERROR = 0;
/** Course automated backup never finished */
const BACKUP_STATUS_UNFINISHED = 2;
/** Course automated backup was skipped */
const BACKUP_STATUS_SKIPPED = 3;
/** Course automated backup had warnings */
const BACKUP_STATUS_WARNING = 4;
/** Course automated backup has yet to be run */
const BACKUP_STATUS_NOTYETRUN = 5;
Am guessing entered only if running auto backups from cron job.
For other questions ... again ...
Alain Raap shared this today:
https://moodle.org/mod/forum/discuss.php?d=383815#p1546885
Shared earlier:
https://moodle.org/mod/forum/discuss.php?d=383012#p1544844
https://moodle.org/mod/forum/discuss.php?d=383012#p1544910
'spirit of sharing', Ken