There's one line on this rebate form that I don't understand. It says, "To receive your $20 rebate by mail, purchase 5 single rolls or a five-pack of KODAK PROFESSIONAL PORTRA 160NC, PORTRA 160VC, PORTRA 400NC, PORTRA 400VC, or PORTRA 800 Film." ... Gee, if that's all that's required, then why do I need to spend $125 on film to get this rebate? What am I missing here?