The last time I brewed with a Foundry Anvil (mash tun and boil kettle the same), I selected BIAB as my mash choice and mashed with the max water amount that Beersmith showed for Mashing in, (no sparge). I yielded the correct amount of wart but the efficiency was terrible. This time I'm planning to pull the mash pipe up slowly and slowly rinse the grains with the Beersmith recommended amount of sparge water. As the wart level rises, I'll slowly raise the mash pipe. I guess my plan is more like fly then batch sparging. And yes, I forgot to take a gravity reading.
The issue I’m having with Beersmith is that it recommends I,” batch sparge with 2 steps (1.65 gal, 3.42 gals) of 168 degree water". Adding these amounts with the mash in amount of water, 2.87gals totals water volume of 7.94 gals. Like you said, I need to check the drain mash tun, but I can’t find that choice in the mesh tab of Beersmith.