Water -- Palmer's Nomagraph Question

[slaman992003]

ON John Palmer's How to Brew Nomagraph, there is a color bar at the top of the nomagraph.

a) What is the difference between the SRM numbers at the top and those at the bottom of the bar?
b) After drawing my line from Effective Hardness through Alkalinity to get a Residual Alkalinity... do I continue the vector of the line diagonally into the color bar? or do I go vertically from the Residual Alkalinity value.

Background for example.
Ca : 33, Mg 10, Alkalinity : 100

This gives Residual alkalinity of : ~60ppm
So if I continue the vector of the line, this gives good SRM values of 16 (on bottom) and 26 (on top).
If I go vertically up from the RA of 60, gives 10 (on bottom) and 16 (on top).

Which is right?

[slaman992003]

Figured it out myself. Thanks. The SRM values on the top refer to when toasted malt is the primary specailty addition and the bottom is when roasted is used.

His tool is setup around RA. You could get the same SRM using different methods, but adding toasted vs roasted has different effects on pH. ....At least that's what I think he means (John?). I had to dig through his NB waterganza series to find it.