It says the drive size is 834mb?!
or that 834mb are used on the disc?
Perhaps its the Lion "Recovery HD" partition. Launch terminal and type
diskutil list
What am I looking for when I do this?
Operating systems and working overheads.
And for why it still says "2TB": 2 TB - 834 MB = 1.999161 TB (SI)
i.e. it's correct to 3 decimal places which is still excessively accurate.