Hi Andrew,
I am not sure if I understood your review correctly, but if you are saying that 10 credits were used for 5 images, that’s the normal behaviour. We say it very clear on the FAQ:
A credit = an optimized image?
Yes, that is correct.
But please note that usually an image in Media Library has 3, 5 or more associated thumbs. Each optimized thumb requires a credit. In the rare cases when ShortPixel does not optimise the image (lossy) with at least 5%, the credit will not be consumed, though.
In any case case, we appreciate giving us your feedback. ??
Have a good day!