Hi,
Total Capacity shown in the media information is the amount of expected total raw capacity of the media. Some tape devices support the ability to read the amount of Total capacity of the media that is currently loaded in the device. If a tape device supports reading of the total capacity amount, then Total capacity is derived from the total capacity amount. Otherwise, Total capacity is estimated based on past usage of the media.
Make sure that the latest Veritas drivers are used. The drive firmware is updated to the latest. Also the compression option is enabled.
Please refer to the technote below to download the latest device drivers:
http://seer.support.veritas.com/docs/265501.htm