They are already supported. There is "B" or "byte" for byte and "bit" for bit. SI-prefixes are case-sensitive, so "G" is for giga, "M" for mega, "m" for milli.

  >>> 6 Mbit/s * 1.5 hours to GB

    (6 Mbit / s) × 1.5 h -> GB

     = 4.05 GB