So you need to break it down further and think about the Roman numerals you can choose from. 70 can be partitioned into 50 and two 10s. 7 can be partitioned further into 5 and two 1s. These values ...

That's Super Bowl 59 for those untrained in Roman numerals ... which means one less than 50. New letters wouldn't be introduced until Super Bowl 100, which would be C. Super Bowl 500 would ...