BS2 defines mash profiles, which allow you to describe various mashing regimens. These profiles allow you to define various types of mash steps (infusion steps, temperature steps, etc), the temperature associated with that step, etc. For an infusion step, while editing the step you can define the water/grist ratio associated with that step.
For example, open the "single-infusion, medium body, batch sparge, no mashout" profile. You will see a single step titled "mash in" (I think). if you double click that "mash in" step, you will see a dialog that includes the mash temperature (152), a few other things, and a water/grist ratio box (1.25 qt/lbs is the default from memory).
There is also a water volume box. In a recipe the "volume" box is calculated based on the actual grist in the recipe. But, in the "mash profiles" list, they aren't connected to any recipe. So, the volume is calculated based on an assumed 10 lbs of grain and your entered grist ratio. It can also work in reverse. In other words, you enter a desired volume and it calculates the grist ratio---not very useful most of the time, but possible if you need it.
NOTE: When you create a recipe, you attach your desired mash profile to it. At that point, all the volumes will be calcuated based on the recipe grains, and the profile grist ratio. Also, THIS IS KEY, the recipe keeps its own copy of the mash profile. It's truly like an attachment to an email. If you change the original profile, it will NOT update the recipe, and vice versa. This catches a LOT of people out. If you ever want to update the recipe attachment, you can simply re-attach the modified profile. This same fact is true for all profiles attached to a recipe (fermentation, equipment, carbonation, and mash).
Welcome to BS2.
