Without seeing their methodology, it is impossible to know if what is being reported is totally accurate. For example, how do they prevent re-entries from being counted again? What about multiple days? Is it tickets sold or do they actually count people in attendance?
Florida, Hamcation counts the turnstile if I recall correctly; so if you go in and out 4 times on 3 days that is 12 entries. Hamvention in Ohio as far as I know counts tickets sold.