I have my 70 qrt. cooler set-up on BeerSmith, and I would like to do a 13.2 gallon batch of 1.056 OG ale. My problem is that I don't understand why the program tells me to mash-in with 8.9 gals, then sparge twice with 6.1 gals? I think the whole sparge water should fit in the tun on one go? What setting should I adjust? Thanks!