So... for instance…. Raspberry(cap) is suggested at 7% and watermelon (cap) at 15%. That's 22% total of flavorings.
Nope, that's not how it works. It helps to imagine that you have two bottles of single flavoring juice and are combining those juices together to make a blend.
Let's imagine that you have a 10ml bottle of Raspberry (cap) at 7% flavoring so it has 0.7ml of flavoring in that bottle.
Let's further imagine that you have a 10ml bottle of Watermelon (cap) at 15% flavoring so it has 1.5ml of flavoring in that bottle.
If you were to dump those two bottles together in a larger bottle you would have 20ml of juice with 0.7ml + 1.5ml = 2.2ml of flavoring. Now 2.2ml of flavoring in 20ml is 11% flavoring, not 22%.
This is completely imaginary as you can make a great watermelon by starting with your watermelon flavoring fairly close to its stand-alone % and adding a half-dash of raspberry.
It sometimes helps to mix single flavoring juice and get them close to the taste you want, then mix those together and reverse engineer the contents to develop the recipe if one of your combinations comes out great. This means you have some vapable, the single flavoring juice, to vape while you work on greatness while you get a feel for how flavors blend.