Mapping of LFAU to disc size

LFAU     512 byte secs     1024 byte secs
----     -------------     --------------
256      up to 124Mb       up to 127Mb
512      up to 249Mb       up to 255Mb
1024     up to 503Mb       up to 511Mb
2048     up to 1007Mb      up to 1023Mb