Google PageSpeed Insights slow responce time for styles-thumbnails.php

Fistly, thanks for the great plugin. Looks and works great.

I continually get a suggestion from Goolge to improve server responce time and this link is always the culprit.

https://thegreenmanproject.com/wp-content/plugins/yet-another-related-posts-plugin/styles-thumbnails.php?width=120&height=120&ver=4.0.6

Any idea as to how I might fix this?

https://www.ads-software.com/extend/plugins/yet-another-related-posts-plugin/