Do you know the date interest is calculated from? Interest isn't calculated from the date of the issue of the PCN. Interest is calculated from the "past due" date of the PCN. Do you know when that date was? Have you calculated the interest on the principal sum or on the total sum which includes debt recovery fees and or damages.
Based solely on the information in the PoC, how on earth can you calculate anything? The PoC state that the PCN was issued on x/x/xx. No it wasn't. The PCN was issued after they applied for the Keeper data from the DVLA.
What does PoFA 9(4)(5) say about the charge?
Stop using ChatGPT as though it is infallible. It is very error prone when it comes to doing a simple comparison to things, especially when it cones to UK law.