One likely candidate would be that the words for “thousand”, “group of people”, and “chieftan” are all written as 'lp, hence one option that has been tried is if all of the “thousands” in the list are the numbers of family groups, one ends up with ~5,000 adult males, and thus ~20,000 total. Which happens to also be about the size of the documented population increase in the hill country of Palestine c. 1200 BC. An influx of people with somewhat different pottery and very few pigs.
were the citations for that (from a compilation book we have).