Remember to use the correct default settings also in HDTOOLBOX, as OS3.9 gives the correct size of the disk.
So for example if your drive is 74.3GB in size but HDToolBox shows it as 68.3GB, AmigaDOS measures in numbers that are meaningful to file system, powers of two. A GiB,the proper ISO term, is 1024*1024*1024. If you multiply that by the 68.3 you get your 73,336 million bytes.
Also check your mask settings.
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