I wouldn't worry about the discount, the allegation on the PCN is the wrong one.
Looking at the photos, I can see why the PCN was issued:


However given the appearance of the location on GSV here
https://goo.gl/maps/yzcTNVjPGuEQ3NVA6 it is clear that the kerb is not lowered, it's the carriageway that has been raised. It is also not at all apparent that it has been raised for any of the statutory purposes listed in section 86 of the Traffic Management Act, rather this looks like a traffic calming measure.
Draft representation:
Dear Newcastle City Council,
The contravention alleged, "27 - Parked in a special enforcement area adjacent to a footway, cycle track or verge lowered to meet the level of the carriageway", did not occur.
At first sight it appears the CEO might have wanted to issue a PCN for "28 - Parked in a special enforcement area on part of the carriageway raised to meet the level of a footway, cycle track or verge", but that is not what is alleged on the PCN and the council cannot now amend the allegation.
In any event, having reviewed the location, it is not at all apparent that the carriageway has been raised for any of the statutory purposes listed in section 86 of the Traffic Management Act 2004, rather this appears to be a section of carriageway that has been raised as a traffic calming measure.
In any event the contravention actually alleged on the PCN did not occur, and for that reason the penalty chage must be cancelled.
Yours faithfully,
Make representations online and make sure to keep a screenshot of the confirmation page.