Adjusting the Width and Size of Thumbnail?

This is actually a great plugin…I mean all in one related post with the related contents at bottom and can be shown as a widget…

However, my problem is adjusting the size of the thumbnail…

I’m using the widget and the thumbnails are too small for the Widget-Area Width.

How do I increase the size of the thumbnail?

There should be an option for this in the Setting.

http://wordpress.org/extend/plugins/yet-another-related-posts-plugin/