Ratios are not perfect, nor are absolute numbers, except that I have found that you can get to "alka seltzer" quickly if you get too heavy handed. These numbers seem fine for a 5 gallon batch, but mine would be dialed back a bit for my tastes. Maybe 6 g CaSO4 and 3 g CaCl2. Of course many APA's are now pushing IPA hoppiness, so it just depends on what you are shooting for... In any event, you are in the ballpark and can adjust as you desire on your next beer.