how its determining whats the most viewed

Hey, I’m using your plugin called Popular widget.. works and everything I just have a question about how its determining whats the most viewed.. and where the information is being saved.. is there some log file somewhere or whats going on… the reason im asking is I dont want something to be building up in my website getting too large.. I noticed when i uninstalled the plugin and reinstalled it the info on what was the highest viewed was saved and the posts reappeared.. Please let me know thanks for the plugin BTW. helped my site alot

jason