@slomo here's a draft:
Dear Hampshire Council,
The penalty demanded exceeds the amount due in the circumstances of the case. This is because I parked my car prior to 10 am, the restriction came into force at 10 am, and by virture of regulation 5 of The Civil Enforcement of Road Traffic Contraventions (Approved Devices, Charging Guidelines and General Provisions) (England) Regulations 2022 the only penalty due at 10:09 am was zero.
Yours faithfully,
Send this online and take a screenshot of the confirmation page.