Thanks for looking and commenting guys... I appreciate, and obviously need, the feedback!
I'm using the online calculator at brewersfriend.com (since I use that for recipes, and it imports my grist and volumes right into it), and had it set for "add salts to mash only". I had it set for 7 qt mash and 7 qt sparge, for 3.5 gal total water used (looking for 3.25 pre- and 2.75 post-boil, to put ~2.5 gal into a 3 gal carboy). I assumed the numbers it was giving (and what I quoted above) were for the mash only, but they are indeed for the total volume. I did then change the sparge vol to 0, so then the total was the same as the mash, and the same additions did show much closer to what AJ calculated above. [And for reference, remember, if it matters, that I'm doing BIAB, with a mash in one pot, then a 10 min sparge (dunking bag, then stirring some) in another pot, and then combining the two "runnings" - can you still call them that if they're not being run off?!
- into the larger pot for the boil.]
So this tells me two things at this early point on my water chemistry education - I need to know the software I'm using better, and, more importantly, I need to have a better general understanding of the subject! To wit: I guess I don't know whether the mineral counts matter more for the mash, or for the finished beer. I was under the impression that it was the pH that mattered more for the mash (with the beer pH usually falling in line from a good mash pH, and also knowing of course that the mineral additions affect the pH), but the amounts of the minerals mattered more for the final taste of the beer (Cl and SO4, Na, etc) and the fermentation (proper Ca for the yeast).
Obviously, they are all tied together and all important, but am I looking at it wrong? Or, asked more to the point - what volume should I be using to get the water profile numbers that are quoted/recommended for different styles (i.e., the dry stout numbers Martin mentioned above - thanks for that, by the way!)... the mash volume only, or the total (mash and sparge) volume? Or should I be treating my sparge water the same as the mash water, in which case the mineral additions would be proportionate to both volumes, and the numbers wouldn't get "watered down" when applied to the full, more dilute, volume? I've read that sparging with just RO is okay (don't want sparge water to be too acidic - which the Ca+ does, right? - to minimize tannins/astringency in the lower gravity second/sparge runnings?), and it makes things easier on brew day. But, it wouldn't be that much harder to measure out twice each addition, so I could easily do that if needed.