Among the lists with at least one follower, how many were created by user who was subscriber when created the list?
lists with at least one follower refers to list_followers > = 1; was a subscriber refers to user_subscriber = 1
SELECT COUNT(T1.list_id) FROM lists_users AS T1 INNER JOIN lists AS T2 ON T1.list_id = T2.list_id WHERE T2.list_followers >= 1 AND T1.user_subscriber = 1