Well I don't a see an E-2 after the 2.83 and I can't make the math work without it...
 
OK Lets check their math as stated on the bill
 

From the statement on my bill (above) we get
Used kWh = Units x 2.83 x 1.022640 x 39.3 / 3.6 = Units x 31.5936106 i.e.31.5936106 kWh/Unit

From my bill the used Units = 217
therefore used kWh = 217 x 31.5936106 = 6855.8 kWh
Well this looks ok too (same answer as they give). At least it had better be correct it is what I am paying for...
OK lets check my math


Volumetric conversion...
1 ft = 0.3048 m (about 30cm seem right ?)
therefore 1m^3 = (1/0.3048)^3 (ft^3) = 35.31466672 ft^3
so to convert from ft^3 to m^3
m^3 = ft^3/35.31466672 or as they would have it
m^3 = ft^3 x 1/35.31466672 = ft^3 x 0.028316846 or as I would have it
m^3 = ft^3 x 2.832E-2
That checks out ok note the E-2

The Expansion Factor
The following link explains the 1.022640
http://www.prnewswire.co.uk/cgi/news/release?id=51151
the figure is as I explained because the gas is compressed the figure is 1.022640 with no exponent (i.e. no E+2 here)

Gas Energy Content
Kinda difficult to prove this one without lots of sodding about but the figure from the net is 39,300 kJ/m^3 or 39,300,000 J/m^3 or there about I have seen similar but differing figures on a couple of sites... Not that proves anything...

Conversion from Joules to kWh
Watts = Joules / seconds
Therefore to convert joules used to kWh you divide Joules by the number seconds in an hour i.e. 3600 giving watts and further divide by 1000 to convert to kW

So to the conversion
so if there is 39,300,000 joules in 1 m^3 then there is 39,300,000 x 2.832E-2 = 1112976 joules in a ft^3
to convert this to kWh divide by 3,600,000 i.e. 1112976 / 3,600,000 = 0.30916 then Slip in the expansion factor (we must ensure a profit for them) 0.30916 x 1.022640 = 0.31616 kWh/ft^3

NOT 31.593 as stated by their figures ????
never mind the numbers it the decimal point that concerns me
so what the **** is going on...

Lets take a look at my Gas meter
 
 
 
My Gas meter says it reads directly in ft^3 not hundreds of ft^3
Or Does it
On the meter I see White number and red numbers while this on my electric meter, car odometer and most other meters this implies numbers after the decimal point. There is no actually decimal point shown on the face (the first hint). Also look at the Clock dial at 6 o'clock there is 0.5 and at 12 o'clock there is 1. It is reason able to assume one revolution of the clock face would increment the right most counter digit by 1. This would in turn imply that the right most digit was in fact unit of ft^3 and the next left 10s of ft^3 so the number in WHITE are in fact HUNDREDS of ft^3... (Second BIG hint) and a careful look at my Bill and the wording says UNITS USED not ft^3... so the 31.5936106 they use is in fact the number of kWh in 100ft^3... Confusion over...