How to determine if the images on the site are optimized?

Question

Search Engine Optimization

I measured the site: https://developers.google.com/speed/pagespeed/insi...
Writes that the pictures on the en/ subdomain are not optimized - links to photos that I have already compressed and re-uploaded.
_________
I checked the en/ subdomain separately on the first service.
Links to THESE pictures are not shown (they say everything is ok with them)
https://developers.google.com/speed/pagespeed/insi...
___
I checked with another service: https://varvy.com/pagespeed/
(there is a window below optimizing images with thumbnails and image titles)
Here it says that everything is optimized.
How can I tell if images are compressed?
How so?

Answer 1

Issue resolved!
It turned out that when transferring the site, the developer did not re-upload the pictures and they refer to a subdomain.

Answer 2

Images must be in the size in which they are indicated in the container, that is, if 1024 * 800 is indicated in the container, then the image must be the same in pixels. And the compression (when saving from Photoshop) must be selected so as not to ruin the picture with artifacts, and at the same time set the minimum possible quality value.