Parking charge for exceeding time limit when i didnt exceed limit

Hi.
I parked in a retail car park managed by Euro Car Parks.

The car parks signs and the website both state the maximum parking time is 3 hours.
I parked there for 1 hour 45 minutes as confirmed by the letter below.

I received a Parking Charge Notice letter in the post from Euro car parks which states: "Contravention: Your vehicle has overstayed the maximum time period allowed"

I was significantly below the time limit however I do not have a receipt and cannot get one.

What can I do here?

Please read the “Read this first” thread and then following the advice in that thread, show us the Notice to Keeper (NtK) making sure to only redact your personal details, the PCN number and the VRM of your vehicle. Leave everything else visible, especially all dates and times.

Is parking free or chargeable?
What other conditions e.g. customers only minimum purchase and enter VRM using barcode on receipt, not 24 hrs and you parked when not permitted therefore no period allowed etc?

photos of the signs at the car park would be helpful as well.