Ok so here is my problem. My boil kettle isn't big enough to hold all the wort from the mashtun its about 5.73 liters short. How do I use the program to just add water after say boiling for 30 minutes to top this up and still hit my final gravity at my post boil volume? I tried top up fermenter but that did not work. If i use top up boil kettle it says nothing. My mash tun is 75.71 liters and the boil volume says 81.44 L. Why would it not give you a pre boil gravity at 75.71L? That way you can calculate the the amount of top up water?