These go by plate number. One benefit is if you pay for 2 hours for example you do not have to stay in that parking space. You can leave and go to some other location. In fact you cannot stay in the same place for more than two hours; that is a separate ticket. It's possible to get two tickets if your time has expired and you stayed more than two hours.
I have no reason to go downtown between 8 and 5 weekdays so I've never dealt with the system. In fact other than my favorite espresso place I have no reason to go downtown except I sometimes enjoy walking around and seeing which businesses have survived. It was different thirty years ago before everything moved to strip malls.