Grain absorbtion in the mash

How does Beersmith arrive at their grain absorbtion quantity in the program. It seems to be low. My recipe had 12 # of grain and the grain absorbtion was 1.5 gal. Ray Daniels book says grain weight x .2. That would be 2.4 gal.

You can set your own grain absorbtion by going  to tools, options, advanced.

Thank you RickS, that is the answer I was looking for. Much obliged.