How many words do you use ?
I find that test somewhat far from the truth. I say this because the test had a particular thing factor that can make it less accurate. You had to pick only the words you knew the by definition. Some definitions are not easy to be given as in some dictionary definitions are still not clear. Then there are those words that you know how to explain with synonyms, but this wasn’t given as an option to pick the words.
It also never gave an option for people to pick the age variable. Someone on in his early twenties won’t know as many as someone in his mid fifties. Someone over sixty won’t remember as many as someone from his mid thirty.
I had a bit above 14k according to that test while I picked only the words I knew how to explain. I don’t find number small or too big but I’m sure I’d understand anyone no matter what words they’d use.
Do you use many words daily? Do you use only words that you know how to explain or you just use them because you know they have synonyms you know how to explain? How varied are the intellectual levels of the people you interact with on a regular basis?