Vault - Disk to Tape

Hi Guys. me again. I am backing up to disk. I am using vault to write from my disk backup to tape. Attached is the vault summary. It seems to me that vault is writing only 1 or 2 images to most of the tapes. The tapes are DLT 1.6 TB. I see that the images are less than 1 TB on most of the tapes. This is causing the backups to be written to 26 tapes. How can I configure vault to fill one tape before moving on to the next tape.