I created a media set report in the reports tab.

On a few of my tapes. I know that it had FAILED the backup

I see the cartridge (tape name) and at the end Write MB and Current MB

On some I see write MB has been 21,434 - 20Gigs with a current MB of
824MB
and some with
10345MB - 10 gigs with current of 185MB.

How does these tapes work ? When you wrote something to it, and only
824MB
is currently on it, with 20Gigs written, does that mean the tape is full
or I can put more data on it ?