Also, per a thread on SCT's forum, not all Xcal II's have the same equation on the flash tool. Apparently the later 'blue screen' ones are different than the early ones.
Early analog equation: (v*3)+7.35
Late analog equation: (v*13.29)+7.35
I don't think I'm allowed to quote the post from the SCT forum or I would have, and unless you have PRP you aren't allowed access to it.