Expired Job on Backup exec 2014 refuse to delete from the storage

To free space on my storage disk, i needed to delete jobs before the retention period reaches. When i expired the job from the backup exec console, within few seconds it delete automatically.

But unfortunately the size of the disk storage still remain the same, no space was freed despite the job been deleted. What can i do to free space on the disk storage after i had expired the job on the backup exec console?

I will appreciate a quick response.

Thank You