Hi,
This indicates that you set the "image width" and "image height" settings of the HikaShop configuration. These parameters allow you to have HikaShop automatically resize images when you upload them.
So since that's not what you want, you want to keep these fields empty in the configuration, like they are by default.
It also means that the images your uploaded so far have been resized on upload, and you'll have to upload them again if you want to be able to see them in their original size when you click on the small size version of the product page.