I just went on Priceline.com and found a great offer: Round trip airfare from New York to Washington plus a?

rental car for just $284 ( taxes included). The only problem is that it says that I have no confirmed departure time. I can fly anytime between 6am. and 10pm. Does this mean that I have to be at the airport on standby for 14 hours each way?!!! How does this work, exactly? There is no specific info on their website as to how this works.