I like to show more than 5 popular contributors on the side bar widget in topic view. I toggle the option from front end widget control to make it 10 or 20. It's only increasing this numbers for week, but not for month, year and all time which remains fixed at 5.

If I move this widget on main body above the topic it's showing up to 15 (not 20), but not in the sidebar. Anyway possible to fix that?

It's definitely a bug. Please post here too: https://community.invisionpower.com/4bugtrack/active-reports/