The one on the left is for half an hour and the one on the right is for an hour use. Whenever you are parking your car on the street, you need to scratch the date and the time and place them on the dashboard of your vehicle.
For instance, if your going to be parking for an hour and a half from now, you need to scratch off the date and the current time for the 1 hour card, then you also need to take out the half an hour card to scratch off the time as a continuation. Place them on the dashboard and you are all set!
People on the motorcycle will be checking these card against the front window. If you were unfortunate and received a ticket, the penalty will be 100RM or 50RM if paid within a week.