They do sound the same to me, but I wouldn't use the term self-service in this context. I think we'd normally refer to them as convenience stores - usually smaller than supermakets, but still with the concept of helping yourself to what you need (rather than being served).

I think you would need to check with the client to find out their exact definition of each, in order to find a differentiating word in English, such as grocery shop / small shop etc, because they do overlap but they obviously are differentiating them here for their own statistics.