Yes, 10 minutes from 08.43 takes you to 0.53, so the PCN should have been served on or after 8.54. If you want to take the matter further, (i.e. no pay the discount), you must wait for them to serve a Notice to Owner.
so are you the owner and if so, is your name and address on your V5C Registration Certificate, (aka Logbook), up-to-date ?