beersmith calculates this one at 1.072
we talking dry or liquid extract? they have a different potential SG, which may account for some discrepancy.
and is that 6 2/3 lbs of extract or 6 lbs of 2:3 extract?
style guidelines for SG are 1.044 - 1.056, so shoot for something in that range by changing the amount of wheat extract
also, IMHO, i would avoid the roasted barley in a dunkelweiss, that will make it too roasty.