Backup Exec - how can you tell how compressed the data is?

I am using BackupExec V8.5 on an NT server w/ a DDS4 tape drive.  Nominally, the tapes are labeled as 20 / 40 gig.  how can I tell the compression I am getting?  I used to be able to store 36 gig successfully on 1 tape.  But in the last couple weeks, the drives being backed up have ballooned to 53 gigs (gotta get the users to not store their MP3s on the server : ) !  The backup is now asking for another tape after it says it backed up only 22 gigs!?  and it's set to use hardware compression if available otherwise software.  is there a way to tell it to use the one that works best (highest compression) or do you have to experiment for yourself?  

That bruce PST error is because it's open.  Getting past that error / having it back up the open file / skip the open file is another issue...

Here's parts of the log:

======================================================================
Job server: NTSERVER
Job name: Full backup L, N, S
Job started: Tuesday, February 14, 2006 at 5:17:31 PM
Job type: Backup
Log file: BEX596.txt
======================================================================

Drive and media information from media mount:
Changer Name:
Drive Name: SEAGATE 4
Media Slot: 0
Media Cartridge Label: 2006-6
Targeted Media Set Name: Media Set 1

======================================================================
Job Operation - Backup
Media operation - overwrite.
Hardware compression enabled.
======================================================================
Remote Agent for Windows NT/2000 not present - performing standard backup

Media Name: "Media created 2/14/06 05:17:31 PM"
Backup of "\\SNAP\L "
Backup set #1 on storage media #1
Backup set description: "Full backup L, N, S"
Backup Type: NORMAL - Back Up Files - Reset Archive Bit
Backup started on 2/14/06 at 5:18:45 PM.
File "bruce.pst" in use - Backed up.
WARNING: "\outlook\bruce\bruce.pst" is a corrupt file.
This file cannot verify.
^ ^ ^ ^ ^
File "archive_bruce.pst" in use - Backed up.
WARNING: "\outlook\bruce\archive_bruce.pst" is a corrupt file.
This file cannot verify.
^ ^ ^ ^ ^

Media mount failed.
User aborted a Physical Volume Library operation.


Backup completed on 2/14/06 at 11:08:12 PM.
Backed up 100664 files in 9919 directories.
2 corrupt files were backed up
2  files were in use
Processed 22,677,682,101 bytes in  2 hours,  52 minutes, and  25 seconds.
Throughput rate: 125.4 MB/min
----------------------------------------------------------------------

======================================================================
Job ended: Tuesday, February 14, 2006 at 11:08:12 PM
Job completion status: Failed
======================================================================