And this is when you need someone to say
"Ignore all that guff about Residual Alkalinity, and any warnings that come up"
Just a hint, a Burton profile treated to reduce alkalinity (bicarbonate) has a low residual alkalinity . . . Negative in fact, it's not a problem, if you treat your water properly it is actually desired. Another example the 'Pilsen Profile' has low residual alkalinity, in fact you have to lower it further with a calcium salt to help the mash pH fall in the 5.3-5.6 range
. . .Two massively different profiles but with a low residual alkalinity
Residual alkalinity is a calculated value from a theoretical concept, and never one I actually worry about, or look at. I worry about three things
sulphate : chloride ratio.
Get the first two right the mash pH falls where I want it, use the ratio to balance dry/hoppy : full/malty flavours.