first of all thanks for contributing to this wonderful project :)
Here is a discussion about the meaning of "word count".
5000 "Lemmas" or "Words"?
What do you as a russian linguist think about that? How many unique words do we really learn in the russian course? And how do languages like English (no cases) compare to Russian (six cases)? Do learners of English have a better understanding of a random text, if they know 5000 words than a learner of the Russian language?