When using adjuncts, does it matter whether or not you count the amount of the adjunct when determining the amount of water for the mash and sparge. We can do this for any ratio, but for example, lets say the desired ratio is 1.5 qts/lb.

then, if my intent is to use 1.5qts per pound and my grain bill has 10 lbs barley and 2 lbs oats, would it matter if I used 15 qts = (10lbs barley * 1.5) and ignore the 2 lbs of oats when calculating the necessary water; or is it indeed “correct” to use the 18 qts (12 * 1.5) for the proper/desired 1.5qts/lb.?

Obviously, 15 qts would be produce a much thicker/less soupy/harder-to-stir mash than the 18 qts, and my run-off would be less by almost 20%, but with respect to getting as much sugar from the barley as possible, does it matter?

cheers.