adding n-p-k values

im not doing this ok but for example if i have MG 24-8-16 and fox farms tiger bloom 2-8-4 if i mixed them would it then be 26-16-20 or is that not how it works how do you add them if this isn't correct

The N-P-K numbers you see on the container reflect the percentage of those elements that are present in the "unmixed" nutrients. Those percentages represent the amount of "Active Nutrients" vs "Filler Ingredients".

If you combine equal doses of "Brand-A" with "Brand-B" (both straight out of the container) - you wouldn't add the two figures, you would average them out and get 13-8-10.