See the quotes...

At that time I wrote this excerpt:

  > I observed the /dev/sda disk that comes with our VM is supposed to be 80 GB big.
  > If this was to a decimal base, it would be exactly 80 000 000 000 bytes big, but
  > it is actually 81923145728 bytes big. That is 80.003072 GB if you define a GB as
  > 10^6 \* 1024 bytes and add 3 KiB (3072 bytes). This is quite non-standard, because
  > you basically mix bases without any sort of transparency.
  >
  > We also have a volume mounted. /dev/sdb is currently 70 GB big where you seem to
  > define a GB as IEC GiB or 2^30 bytes.