Did you get into the university you wanted ? Is this grade going to prevent you from achieving anything you wanted ? If no, then don’t ask for a remark because it’s not worth it. I got a C in biology and A* A in my other subjects and got into my firm choice. I didn’t ask for a remark because my objective was to get into my dream university which I achieved, so there was no point in doing so. If you got rejected because of your grade then do it, but otherwise don’t.