For whatever reason, Beersmith decided to have me lauter my all-grain recipe with an exorbitant amount of water. I don't have the exact recipe in front of me at the moment (can provide details later if necessary), but from what I recall looking at the brew steps, I was aiming for a 6 gallon batch, and it had me mashing with 4.5 gallons, sparging with ~9. I knew something was off when I looked at the brew step that said I should end the boil with 7.5 gallons, to achieve a 6 gallon amount for fermentation.
I have no idea how these numbers came about, but I certainly did not sparge with all 9 gallons. Maybe 7-8, and my pre-boil gravity was well under what Beersmith estimated. It was a batch sparge, no mash out. Again, I can't provide specifics at this very moment, but instead of correcting that recipe, I was more curious about what can be done in the event that your pre-boil gravity is lower than expected?
In my case I had between 7 - 8 gallons going into the boil kettle, I just let it boil down for about 1 - 2 hours before I began my hop additions. In the long run, surprisingly I wound up at about 5.5 - 6 gallons of wort to go into the fermenter when it was all said and done, but what is the normal method for correcting an under-shot pre-boil gravity? Is sacrificing quantity the only way of correcting this sort of shortcoming?