The "Tape" in "Tape0:0:2:0C" is quite normal for Windows OS. I think this has come from the Windows driver, not DP.
About the tape capacity reported... For new tapes DP initially assigns a default value (decided by a global file setting). Once DP has filled the tape with data it will note how much data it got on that tape.
That value (how much data it got on the media) will be recorded and then used by DP in the future when estimating how full the media is.
When protection of the data on the media expires and DP overwrites it, the nominal size for that media will be "how much data it got on the media last time".