Adrotate tracker table too big

I noticed the adrotate_tracker table on my database is too big. About 176MB. It has 4,106,778 rows. I checked this URL http://wordpress.org/support/topic/huge-database-1?replies=14 and I updated the version of adrotate and activated it but the size still remains the same. Did I do something wrong? Is it normal to have such a huge table. The table size is creating some issues on our site now. Any help will be highly appreciated.