It doesn't matter.
Most calculators figure 72%, and that's a pretty normal. What's important is your consistency. If you do it the same way every time, and it works for you, and the efficiency is the same every time, then it doesn't matter. You'll brew great beer with the sacrifice of a dollar or two worth of grains.
As you tweak your system, you may get better efficiency, but it's not really that big of a deal.