Quantum DLT 4000 Product Manual page 259

DLT4000 SCSI Interface
First Block Location
The block address associated with the current logical position; the next block to be
transferred between the target and initiator if a READ or WRITE command is issued.
Last Block Location
The block address associated with the current physical position; the next block to be
transferred to the media and from the target's buffer. If the buffer is empty, or has only
a partial block, the same value as First Block Location will be reported. The first block
or filemark written onto the media is at address zero.
Number of Blocks in Buffer
The number of data blocks in the target's buffer.
Number of Bytes in Buffer
The number of data bytes in the buffer that have not been written to the medium.
DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem 8-99