You didn't mention with whom your friend is renting.

A Chrysler 300 6cyl is normally a Premium with Alamo...and a Charger is normally a Full Size.

The Chrysler 300C is sometimes considered a Premium Specialty or Luxury as it has a lot more bells and whistles on it and costs more for the rental car company to purchase. The size of the car is not the only deciding factor in the class of the car. How it's equipped is also a factor.