Brinestone, are you counting just for curiousity, or did your doctor ask you to track? Our doctor asked how many words John knows at his last two appointments, but at the last one I just said, "I stopped counting at 250" and he was fine with that.
I think once a kid is correctly using the same word in different parts of a sentence and conjugating verbs those are more important trackers for language development than exact size of vocabulary. Unless Lego is still seeing a speech therapist for eating, or there's some other reason you need to track number of words.