Problem specify image dimensions

Hi,

I analice my web in gtmetrix and it advice me that i have two images of your plugin that not specify image dimensions. The images are in my second bar as a widget and the images are:
http://www.adelgazarsinmilagros.com/wp-content/plugins/wp-special-textboxes/themes/stb-light/info.png (Dimensions: 50 x 50)
https://www.adelgazarsinmilagros.com/wp-content/plugins/wp-special-textboxes/themes/stb-light/minus.png (Dimensions: 16 x 16)
So, how can i fix it, please?

https://wordpress.org/plugins/wp-special-textboxes/