Nobody knows. since HP doesn't tell us, anyone who answers this question is just guessing. don't worry about it -- hubscores and hubkarma are just parochial mindgames -- as long as your hubs are over 50, they'll keep dofollow tags, which is important, and id you keep them in the 70-80 range they're going to be jnoticed for all but the most competive nioches -- i've had several hubs listed as 'bwest lately just because they had 3 hits in a day!
"she who tells does not know. She who knows does not tell"