I also got something around 70-80k with 95/100 correct words (I don't know or use most of these words, but the later sections have a lot of words with Greek or Latin origin, which made them easy to guess). One of my wrong words was a misclick in the first section, which I think dragged down the estimate quite a lot. You may have done something similar. I assume they use a simple formula where early misses cost you a lot and late misses cost you very little.