ProMash allows you to figure how much sparge water is needed or total water needed. It will default to 7 gals. normally.
When you open up the stand alone "Water Needed Calculator" it will have many boxes to fill in about your equipments defaults.. sparge vessels dead space, total grain used, water to grain ratio (qts/#) used, losses from other equipment, evaporation rate, boil time, and so on.
Once you enter the data for your equipment, it tells you how much you will receive from the mash after absorbtion, and losses from the tun. It also tells you how much evaporation loss you'll have, all boiler, and other equipment losses that you have dialed in.
At the bottom it even has pre-chilled volumes listed, and into the fermenter after 4% shrinkage volumes in red highlghted boxes.
What you do is adjust the sparge water volume (after telling the software about any losses your rig has) and watch the "to fermenter after cooling" box highlighted in red.
When that box reads the proper batch size of the final product. Look up at the sparge amount box.. that is how much you will need in sparge water.