These images sizes are defined by WordPress, and were added in WordPress 5.3. The comments in the source code describe them like this:
These sizes are meant to enhance the way WordPress displays images on
the front-end on larger, high-density devices. They make it possible
to generate more suitablesrcsetandsizesattributes when the
users upload large images.The sizes can be changed or removed by themes and plugins but that is
not recommended. The size “names” reflect the image dimensions, so
changing the sizes would be quite misleading.
The “Image sizes are defined by the current theme” screen from your screenshot is not part of WordPress. It must be from a plugin that you’re using that is not aware of these new sizes and is incorrectly attributing them to your theme. You would need to ask its developer why.
You can stop them being generated by adding this line to a Must Use plugin:
remove_action( 'plugins_loaded', '_wp_add_additional_image_sizes', 0 );
But you really shouldn’t, as they were added for a good reason.