I don't know exactly how much acidity is added, the attached spreadsheet above gives you an idea of how the SRM affects the amount of residual alkalinity you'll need to start with in your water.
The above additions give you a fairly close approximation of what you'd want for calcium/sodium/sulfate/RA in a dry stout. Given the water you have.
"People should not be afraid of their governments. Governments should be afraid of their people." - V
Secondary: Shady Lord RIS, Water to Barleywine, Pumpkin wine, burnt mead
Kegged: Crappy infected mild
Bottles: Apfelwein, 999 Barleywine, Oatmeal Stout, Robust Porter, Robust smoked porter, Simcoe Smash