Well that was a cool test indeed. My estimate came out at 34,200, which seems acceptable for my age of 57 based on the average for a native [American] speaker. The correlation with SAT scores (yes I still recall those after all these years ) was also remarkably accurate. In my defense I did much, much better on the mathematics half of the SAT, and all my education post high school was in science/math/engineering.

This reminds me of a conversation I still recall from graduate school of the various sizes of vocabularies of various types we all have:

vocabulary reading > > vocabulary writing > vocabulary listening >> vocabulary comfort speaking.