As mentioned above, a Surface 4 running Windows 10. I just changed the value to indicate the total amount of water rather than the wort collected. Dang, I'm good, 175% conversion efficiency! The pre-boil efficiency of 136% is realistic, as I had to add 12 ounces of DME to reach my desired OG. When I switch back to the wort collected (4.125 gal), the conversion efficiency comes down to 144% - more realistic considering the DME addition.
Can you explain the math to me? I don't see how total water is relevant to the conversion efficiency unless you are trying to account for sugars left in the mash tun, the assumption that you can (and want to) sparge all of the sugar out of the draff.