I have been around and around trying to fix this and I see others with similar problems but can't understand the solution. I think that the issue might be related to the recoverable mash deadspace which is .92 gal (Grainfather). I started with a single decoction profile and added a temperature step because the recipe called for it. First step is infusion with 1.25 q/lb, all OK. It added the deadspace volume to the mash water volume to calculate the water to add. Next step is temperature, I did not put in water but it filled in water to add -4.1q. I changed it to zero but later it was back. It also changed the water to grain ratio, but I changed it back to 1.25. Error message, can't have negative infusion volume. Third step decoction, again I changed the ratio back to 1.25 and it says add -.88q water. I don't get it...