Are you willing to risk being sued?
OK. Do you accept overstaying?
Did you display the ticket clearly?
Did you take a picture of it in your windscreen?
Would it be possible to give me the information I asked for?
OK. Best of luck with this.
They could establish how much parking you had paid for if the correct registration was entered after payment. However, they generally won't take legal action. For one they would have to prove that you of the terms and conditions of parking because they would have to claim breach of contract. Even if you did know the exact terms and conditions they wouldn't be able to prove that you knew so their case could fail at the first hurdle. I don't think they will sue you. And if they do you have a defence as outlined.