The DLM(Data Lifecycle Management) expiration or a manual deletion of a spanned backup set does not delete some .bfk files if it is spanned across multiple disk storages.
When a backup job runs to a storage device pool which contains multiple disk storages, the backup set can be spanned across multiple disk storages. After the retention period of the backup set expires, the .bkf files on a disk storage which is firstly used are deleted by DLM. However, the .bkf files on the other disk storages are not deleted.
This issue is resolved in Backup Exec 2014 or later versions.
To resolve this issue and receive the new Backup Exec improvements please upgrade to the current version of Backup Exec.
NOTE: Symantec continues to focus on the current release and future releases, there are no plans to address this issue by way of a patch or hotfix in earlier versions of the software at the present time. Please contact your Symantec Sales representative or the Symantec Partner for upgrade information including upgrade eligibility to the release containing the resolution for this issue. For information on how to contact Symantec Sales, please see http://www.symantec.com
WORKAROUND (Backup Exec 2012)
Manually delete the .bkf files left on the disk storage and run an inventory job.
Backup Exec 2012