Yes.. the whole binary vs decimal, 1024^3 bytes vs 1000^3 bytes mess. The reason why a HDD's reported capacity in the OS is generally different from the GB number it is sold under. FAT32 can house up to 4GiB files for a similar reason that 32-bit computers can address up to 4GiB of memory, right?
For SuperDuper I meant that it just failed silently. The program stalled half way through the backup without any error or advisory message. Took me a while to figure out why!