Not resizing on right size

the plugin is not resizing the smaller versions of the gifs in the right way, as you can see on this one: https://trouble.place/wp-content/uploads/2016/09/berlin-tower-tv-car-gif-720×960.gif

the resized image is way bigger than 720×960. this causes huge loading time when this version of the images are called.

is it possible to be fixed?