"Parked with one or more wheels on or over a footpath or any part of an urban road other than a carriageway (footway parking)"

I was talking to the warden and told him that there were other bikes across the road within the lines of the offense and complained why they didn't get a PCN.
All he told me was that "once the parking ticket has been issued all you can do is to contest this to the borough in writing.
Am I in the wrong? Was I rightfully done? Is there something I can do about this???
Thanks