Exchange backup to tape 0 Bytes

Hi,

I'm backup exchange to tape (appended to another file job on the same tape). It all completes with no errors. However when I come to view the backup set for exchange it displays as 0 Bytes. I've attached an image showing the various screens which relate to the specific backup. I believe I read on another post that the '0 Bytes' display is a bug, but I can't find that thread now.

GRT is disabled so I can't expand the store to see what is included and it's tricky for me to do a full restore elsewhere to test it's backed up ok. Exchange manager shows the store as being backed up and all the logs get cleared.

How can I be sure exchange is backed up safely to the tape?

Regards
Adam