This was addressed in program bulletin # 81. When 'user specified' is used for the external insulation H2k calculated it in twice. The workaround is to put the total depth of the insulation all to the inside.
This was supposedly fixed a good while ago, but obviously not! I think that the original problem came about when the external insulation wasn't calculated in at all and the fix was the same, put all the insulation to the inside. This was "fixed" with a following software update.........or not