Well, I guess the two factors may be related, as I don't necessarily understand how you do your calculations.
What I'm after is this: If you mash in with a certain amount of water, and then drain your tun in preparation for batch sparging, the volume of wort that comes out isn't equal to the water that went in. Some of it remains absorbed in the grain. I've seen numbers like 10lbs of grain absorb 1 gallon, 8lbs absorb 1 gallon, etc. Beersmith obviously accounts for this in some manner. I'm just wondering if you use some tweakable constant for this, or if its more complex than that.
Thanks,
Nate