Well they suggest %6 to %9 in total.
I mixed all flavors with fixed %8 ratio and all came out pretty good, for single mixes I don't suggest more than %9.
So if you compare, WF is close to TFA. You can say they are in middle.
The thing is, the percentages they suggest are really accurate and its totally fine by me. Even though the flavors are not super concentrate, if i know that I will be happy with the suggested percentages, its fine.
! Unlike RF SC line. Because I also mixed plenty of RF SC line ( more than 20 )with fixed %2 ratio and they are all tasteless @ %2. I need to add extra flavor, need to spend lots of time again, really annoying.
If the percentages are accurate and if you know what you will get, it's a fair deal for me.