[Plugin: Ad Buttons] Image size fields for a button ?

How do I see the image size fields for a button ?

I’m testing my site (slow) with gtmetrics and its complaining:

“Specifying a width and height for all images allows for faster rendering by eliminating the need for unnecessary reflows and repaints.”

with regards to the images used by my Ad Buttons.

Thanks,

-F

http://wordpress.org/extend/plugins/ad-buttons/