Compression of sprites not working

Dear Community,

in my private project I have a lot of sprites. When I built my game I used the editor log to look at the size of my assets. A bunch of these sprites end up as assets with 2.1 megabyte and a few others end up as assets with 360kb. The only difference between these sprites that I found is the warning in the inspector:

"only textures with width/height being multiple of 4 can be compressed to DTX1 format"

Looking at the size of the jpgs in the assets folder of my project I found that the resolutions of my images are very different and barely any of them have the required 'multiple of 4' relation. Here is what I found: The images that are compressed have ratios of:

• 755 * 1051

• 756 * 1052

• 752 * 1052

• 755 * 1056

The images that are not compressed have ratios of:

• 755 * 1055

• 756 * 1051

• 755 * 1052

• 752 * 1051

Can anyone explain this behavior? I am utterly confused. And since my project of only a few cards has 500mb I want to reduce that size.