Setting Grain Absorption Rate

So, I've been a BeerSmith user for probably about two years now.

I do overnight mashes and have largely used the BIAB Mash Profile for this.  There's no sparge; just mash in with the full volume of water and let it sit for six to eight hours, drain the tun and away we go.

The problem I am having is that routinely I have found that Beersmith's grain absorption calculations put at least a gallon more than what I need.  When I calculate by hand I calculate about .12% and this is usually spot-on for my setup and process.

To a great degree this makes one of the core reasons as to why I like BeerSmith somewhat moot.

Is there a way to change that number?

I measured the mash volume before grain addition and after to get a net grain absorption of water.  You want to make sure this number is stable over a couple of batches.  Convert to fluid oz/oz of grain.  Enter this number in the grain absorption value which can be found under 'options' > 'advanced'.  Be careful with the adjustment of these numbers until you are pretty sure that you are consistent with the absorption rate, as this is a global reference and will affect all recipes.

Thanks!

The number is stable.  Prior to using Beersmith I did all my calculations by hand and had to learn what "that number" is by trial and error and it's the result of probably over 50 batches. 

Since I never do BIAB using it for "Overnight Mash" can be appropriated without too much of an issue.  I'm just happy to have something that works with the math that I know is right for my setup.

That was the one glaring thing about BeerSmith that I could never quite nail down.  Thanks for your help!