Two points.
1. The contravention is not paying to park - you did pay.
2. The 0/O error is common and some adjudicators will laugh this out of the tribunal as allowed because the font used on plates is identical and because of triviality. But some adjudicators feel their hands are tied by the traffic order and can't use mitigation.
You should certainly challenge - Newham has a bad reputation but may allow this anyway.
