My understanding is that the rule put a maximum volume in place for shows. An average show will run the gamut, and may only hit the upper limit once or twice (

My understanding is that the rule put a maximum volume in place for shows. An average show will run the gamut, and may only hit the upper limit once or twice (for example during some action or music sequence). Commercials are engineered to be as close to the upper limit as possible for their entire duration. It doesn't matter that there's an upper limit to the volume, because it sounds relatively much louder than whatever was on just before it, and it sounds as loud as the loudest most exciting and dramatic bits of the show.