I've just finished talking to DFI.
The original value of 0.716V is correct. This is a real figure measured with a DMM, so that's why he said there is some variation from the 0.67% and also the fact that a half measure was used (75) instead of 70 or 80.
I think, because it is only one figure out of the entire set of tables, the best thing to do with that is try it and see. If 0.716V isn't working, try 0.7102V.
And the other thing is, some people might have noticed that their VTT voltage values in the BIOS don't correspond to the second table. Please update your BIOS to 0307 or later and it should match.
That brings me onto the BIOS that was promised to fix the wording for the GTL REF settings in the BIOS. They have double checked everything and the BIOS is correct after all (I think Praz said it was), so the tables have been updated again and as far as I can see, we are all fixed and good to go!
Sorry for any confusion :)
http://www.clunk.org.uk/forums/12436-post11.html