Kaiser Water Calculator, Percent Roasted question

Initially I thought I had an understanding of how to compute the "% Roasted" value for entry into the Kaiser Water Calculator, but now I'm beginning to think I've been doing it incorrectly, How is the proper "% Roasted" entry derived?

This is of direct relevance to the Brewers Friend Advanced Water Calculator also, as it uses Kai Troester's formulas.

I don't use the Kaiser calc but I've used BF for a long time.

Isn't it as simple as determining the grist percentage by weight that is comprised of roasted grains? What do you think you've been doing incorrectly?

In the Kaiser Water Calculator it is explained that base malts are to be excluded, and that it is the percentage of SRM color contribution per unit of weight of the roasted vs. the same for Caramel/Crystal. Where I'm getting confused is in trying to determine if higher colored kilned malts contributions to SRM color should be included or excluded.

Hypothetical example grain bill
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10 lbs 2-row brewers base malt, L = 1.8
2 lbs Vienna malt, L = 3.5
1 lb Munich II, L = 20
0.5 lbs Melanoidin, L = 26
1 lb Caramel 20L, L = 20
1 Oz. Carafa III Spcl., L = 470

Method 1 for % Roasted:
--------------------------------------
1) Exclude base malts 2-row and Vienna, and ditto for Munich and Melanoidin (since diastatically active and sometimes considered to be base malts)
2) 1.0 lbs x 20L = 20 color-lb. units for crystal (not considered roasted per Kai)
3) 0.0625 lbs x 470L = 29.4 color-lb. units for Carafa (considered roasted per Kai)
4) 29.4 + 20 = 49.4 color-lbs total
5) 29.4/49.4 = 59.5% roasted color-lbs

Method 2 for % Roasted
--------------------------------
1) Exclude base malts 2-row and Vienna only
2) 20 x 1 = 20 color-lb. units contributed for Munich (not roasted)
3) 26 x 0.5 = 13 color-lb. units contributed for Melanoidin (not roasted)
4) 1.0 lbs x 20L = 20 color-lb. units for crystal (not considered roasted per Kai)
5) 0.0625 lbs x 470L = 29.4 color-lb. units for Carafa (considered roasted per Kai)
6) 20 + 13 + 20 + 29.4 = 82.4 color-lbs total
7) 29.4/82.4 = 35.7% roasted color-lbs

So it's either 59.5% or 35.7% roasted. In the end, whereas Kai gives one example and specifically states in that example to exclude the color contribution for all base malts and count only caramel/crystal and roasted, he makes no mention of what to do with the higher color kilned malts which are diastatically active and could therefore actually be considered to be base malts, yet still contribute a lot of color-lbs. Mash pH prediction is radically different for Method 1 and Method 2.

When in "color mode", Brewers Friend appears to be identical to the Kaiser Water Calculator. But wherein the Kaiser calculator makes an attempt (albeit confusing and incomplete) at explaining the % roasted, Brewers Friend does not (to my knowledge) offer any explanation of it. Perhaps because they themselves have no real understanding of its workings. ???

OK, from some highly valued assistance I got from a moderator on the Brewers Friend forum, all of the grains percentage of SRM contribution are to be summed up and then the SRM color contribution from the roasted are divided by this total to get the percent roasted. So for my example it becomes:

10 x 1.8 = 18
2 x 3.5 = 7
1 x 20 = 20
0.5 x 26 = 13
1 x 20 = 20
0.0625 x 470 = 29.4

29.4/(18 + 7 + 20 + 13 + 20 + 29.4) = 27.4%

The correct value to place in the % Roasted field for my example batch is therefore 27.4%

It all makes perfect sense to me now.