There are three block sizes that this feature was written for.

512 KB

1024 KB

520 KB

is the standard block size for windows/NT and unix

is used by some magneto optical drives as a technique to increase the amount of usable disk space. Some of the early unix workstation companies like Apollo used the 1024 sector size.

The IBM AS400 uses this non-standard sector size.

Enter the block size that you want and then reformat.