Featured image size

Hi, thanks for a great plugin. I have some issues with the size of the featured image using the plugin, it gets a bit too wide:

e.g.

https://anandamarga.dk/events/prout-convention-2015/

Is there a way I can restrict the featured image size to 650 pixels instead of the current 700?

Regards

Karl

https://www.ads-software.com/plugins/upcoming-events-lists/