The recipe uses 6% total flavoring, and you ended up around 9% - that's not such a huge increase.
You know what you might want to do as you try out recipes... mix just the flavorings in the smallest bottle you have, keeping the ratios the same. Then use that as your flavoring. (
click here for an explanation) That way you can easily increase the total flavoring without having to re-compute percentages or get all the bottles out again. It's handy for me, because my partner and I vape some of the same recipes, but I can't use as much flavoring.
ps - if you're trying any of mine that I describe as lightly flavored, you probably want it at least doubled. Limoncello Torrone Parfait is one I consider pretty strong.