Broken parking meter

On a visit to Boston, I noticed a parking meter with a paper sack over it that said 'Out of Order.'

A sceptical parking officer removed the bag, inserted a coin in the meter and turned the dial. It worked perfectly.

As the officer began to write a parking ticket, the car's owner rushed out of a nearby building.

"What are you doing?" he yelled after a quick glance at the meter

Spoiler:

"There's plenty of time left!"