Does the field for Batch Size indicate the pre- or post-boil volume? On my program, I have the Batch Size equal to the Wort Size. The reason I ask after all these years is that for some recipes, the brewer might have 5 Gal for his Batch Size, while I’ve seen some might have 8 Gal. I always though the Batch Size indicated post-boil volume. :-\
Depends on what your default system setting under measurements, size, and precision are in ProMash. You can always adjust it there. My default is 6 gallons post-boil volume of wort prefermentation, based on losing 0.5 gallons in kettle and 0.5 gallons in fermenter for 5 gallons of finished beer. I usually bump that up to 7.5 gallons post-boil for really hoppy beers like an IIPA. Obviously this can be adjusted with the arrows and locked to keep all ratios the same. If you click on the pre-boil button in your recipe it will give you your preboil volume based on evaporation rate and time to achieve your desired volume.
I make my batch size same as my wort size, and then in the “water needed” section set for that same volume in the field “after chilling” to fermenter(s). With a little trial and error, the rest for me is setting the efficiency setting in the “edit Ingredients” section so that I get the volume and SG I’m shooting for. At least this is the basic approach for me, and works most accurately when I have few losses from wort left behind in the mashtun/kettle/other also as figured in the “water needed” section. I often refer to past batches to recall what efficiency to expect based on the predicted OG.
edit: What that wort size volume is depends on how much beer I am making, usually 11 or 12 gallons.