I would not be too concerned with the numbers.  This could be related to retries that are occuring at the hardware level.

To make sure that your data is valid on tape, always be sure to set the VERIFY option in Backup Exec.  It defaults to ON, so it should already be verifying the data sets after the backup is complete. If the verify operation is successful, than the data on tape is valid.

Thanks Richard for your posting. Our Verification process always is successful when run each day after the backup.

Thanks again

Pierre