Are you using ShortPixel Adaptive Images (SPAI) configured with your own CDN and noticed a substantial increase in the number of credits being used? Moreover, can you see the same image on the Optimization Report with lots (dozens) of slightly different widths and are you asking yourself what's going on?
Here is the reason why you are experiencing this: Your website is using a (very) responsive theme. This means that for a single image, there are many different versions of it (with different widths) being generated in a small period of time. While this is ideal from an end user/SEO point of view, we understand that it is not ideal for you in terms of the number of credits used.
To minimize this, you can use the feature "Size breakpoints" on the plugin, located on Settings > ShortPixel AI > Behavior. It will allow you to not generate as many precisely sized thumbnails but instead will use some ranges. For example, instead of having 3 different thumbnails with widths of 345px, 370px and 381px, you'll only have a single thumbnail with a width of 400px. For more information, please check this article: Settings – Size breakpoints – ShortPixel Knowledge Base