What you're probably seeing is both normal storage space being 'off' (reported differently) and hardware devices reserving memory.
Devices reserve certain amounts of memory for themselves, this is why the maximum memory reported is lower than expected. Although, 1 full GB seems a bit much.
As for the hard disk space, some may be formatting and partition data and some may be a difference in exponents used by the operating systems (150,000,000,000 bytes would be about 139.7 GB reported by windows, depending on which OS reports a GB as 1,000,000,000 bytes or as 1,073,741,824 bytes)
