You need to make sure your brewpot is set up correctly. This way you don't need to use the water added calculator and based on what is in the recipe beersmith considers the volumes and adjusts accordingly.
So for instance I have my brewpot set up as a 10 gallon pot... I set my batch size for 5.25 and for me, I have a very wide brew kettle, I set my evap to 18-20% depending upon how windy it is... Evap really depends upon a few factors so you have to experiment a bit there.
So, as long as your final volume is less than the kettle volume + the water that will evaporate + whatever is left in the trub 1/2 to 1 gallon usually depending upon your equipment and the recipe maybe more maybe less then Beersmith will produce a brewsheet that tells you exactly how much water to use and when. For AG people it figures the amount of water the grain will soak up and compensates during mash outs and/or sparge(s). Right on the recipe screen next to your 'batch volume' input if you have 'calculate water needed based upon equipment' checked it will show your total boil volume in gray. For me after I dialed in my kettle this has been very accurate. The only variable I have a hard time figuring is with a new recipe the amount of trub left over. So final volume(s) are sometimes in question. But, as long as I hit my final gravity I just stop... So let's say I was trying to make a 5.25 gallon batch at 1.040 OG and I'm at 5.25 and it is at say 1.039, I'll just keep boiling until I get a 1.040 reading (as you boil down from a full boil the wort's gravity concentrates as opposed to what most 'less than full boil' brewers are used to where they add water to dilute the gravity) So I may end up with 4.8 gallons or something.
Now, I set up my equipment first in beersmith, make it the default equipment after you set it up (in tools/options) and then when you start a new recipe make sure your equipment comes up... then start to add your ingredients. You can tweek the equipment from the recipe view and change the volume of the brewpot there however, it will not rescale the recipe if you change the brewpot after you have already put in the recipe. To do this correctly you can go to the scale option and change the brewpot there and it will work...I have to do this if I realize after putting in an entire recipe that it is windier than I thought or less windy or warmer, etc. etc. So I go to the scale option and tweek my brewpot there, changing the evap and THEN it will actually change the ingredient amounts to compensate for the new boil volume. You have to scale if you want to keep the OG targe and the IBU targets the same. So if you don't scale the brewpot will change as will those values and that changes the recipe, if you scale you don't change the recipe's intent just the amount of ingredients...
Hope this makes sense, and the short answer ;p is beersmith does the calculations but you have to set your brewpot up correctly and preferrably do it before you set up the recipe and if you do it after make sure you adjust the brewpot in the SCALE program and not in the recipe or you will change the intent of the recipe.
