Quick question, on BrewMate is the batch size pre or post boil?
Post boil I think. If remember right need to click on 'Brew Day' to get pre figures.
+1 on what Jacob said.
Just to add - the batch size in Brewmate isn't strictly speaking the post boil volume, but is the post boil volume minus losses due to trub and chiller, and any cooling loss from evaporation. The software lets you adjust these losses depending on your system, so may take a few brews to dial it all in accurately.
Simply put - if you want 23L in the FV, then enter 23L for batch size, and as Jacob says click on the 'Brew Day' button to adjust for any losses, grain/water ratio, etc. and calculate your total water required.
Cool, cheers lads. May just play around with it so.