"testing done at recommended usage levels" does that mean they test after it's mixed with Pg/vg???
All reports / info in tables above are based on ORIGINAL liquid in a bottle that you buy (= not in your mixes). This was the first thing to check for me (not saying that all is 100% true everywhere, but i would realise the misleadings if they were any, since those are not that difficult to find). Most companies are using independent companies for testing, to get proper results.
I also added a calculation, how can you check the amount of diketones in your mixes (check FLV section). Example: their Coconut contains the largest amount of Acetoin of all their flavors (2,800 ppm = 0.28%). FLV flavors are super concentrates and you use them at 1-2% usually. It means, that when you use 2% of FLV Coconut in your mix, then the result is 2,800 ppm x 0.02 = 56 ppm of Acetoin in your vaping liquid (which is 0.0056%).
FLV Coconut flavor contains has also 187 ppm of Natural Diacetyl (Natural Diacetyl in some flavors is formed naturally during the flavor extraction process; it can't be formed in large quantities naturally). So, when you use 2% Coconut in your mixes, that means 187 ppm x 0.02 = 3.7 ppm (which is 0.00037%). Completely irrelevant if you ask me and usual testings wouldn't even show any traces of ND in your mix.
Another example: TPA Coconut Extra. Their report says <10% of Acetoin in this flavor (could be either 100 or 100,000ppm; but we assume it certainly is more than 5%, otherwise they would write 'up to 5%', right? So let's take the middle number 7,5% in this calculation = 75,000ppm).
TPA flavors are not so concetrated, so let's use 3% on Coconut Extra in our mix and that give us a result 2,250ppm of Acetoin in our mix (40 times more of Acetoin then in our Coconut FLV mix above). And if you're making Castle Long V2 recipe http://e-liquid-recipes.com/recipe/58929/Castle%20Long%20Clone%20V2 for example, then you also need Brown Sugar, which has <5,000ppm of Acetoin and <5,000ppm of AP. And if you use 2% French Vanilla Deluxe TPA instead of vanillin, this one also contains 10,000-50,000ppm of Acetoin and up to 5,000 ppm of AP.
Another example: http://e-liquid-recipes.com/recipe/99179/Bust-a-Nut recipe, which is also one of the most popular recipes (I love your recipes @Alisa).
5% Sweet Cream FW (67,551ppm > at 5% that is 3,377 ppm af acetoin in your mix)
7% Hazelnut FW (9,950ppm > at 7% that is 696 ppm in your mix)
3% Bavarian Cream FW (1,140ppm > at 3% that is 34 ppm in your mix)
Butter Pecan FW (which imo suprisingly has no diketones)
Sucralose FW with no diketones (but sucralose is not that good for vaping; personally i would avoid it)
Alltogether your Bust-a-Nut mix contains over 4,000ppm of Acetoin. But it is delicious.
You should also be aware, that many premium liquids are also using flavors of these companies above, so you may want to check reports from their testings if you care about diketones.