can’t change image size?

Hi,

I keep getting the “serve scaled images” with gtmetrix with the images from this widget? The suggested size from gtmetrix is 360×450, but when I input this as custom and change the width and height to the above, I still get this notification from gtmetrix? The images are not adaptive? How can I get the image size smaller (without loss of quality) so that my site is faster? Can’t seem to change/customize the size? Thanks!

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