As seen (defined) in your Advanced Options/Backup Life section:
[ ] Force Expiry. If checked, the backup will be retired according to schedule and may cause early retirement of dependent incremental or differential backups. If unchecked, the backup will be marked for retirement on schedule, but removal will be deferred until all dependent backups are ready for retirement. See the NetVault Administrator’s Guide “Backup retirement” section for information on retirement.
As seen (defined) in the Admin Guide:
Force Expiry: By default, if a backup has any dependent backups, its retirement is deferred until all dependent backups are ready for
retirement. You can select this check box to retire a backup according to its retirement schedule. Forcing this behavior can cause early
retirement of dependent Incremental and Differential Backups. To apply this rule globally to all backups, you can modify the Media
Manager settings. For more information, see Configuring retirement rules for dependent backups. If the Retirement Timing Control
option is set to Force Always, the Force Expiry is option is used, regardless of state of this check box.
