Selected image in the slider

Hi,

I have installed your excellent plugin on my website, it’s OK but I have a question for you :

– How images are selected for the slider ? I see that the name is xxxx-308×146.jpg, why “308×146” ? Can I change it ?

The website : http://www.it-connect.fr

Thanks.
Florian

https://wordpress.org/plugins/recent-posts-slider/