There's got to be some highly technical definition of advert

The standard US half hour programme seems to be 20 or 21 minutes long. Similarly the standard hour programme seems to run for 40 to 42 minutes. Check any DVD you have. So, picking the first thing I can spot on the TV schedule, when Five show The Mentalist tonight between 9PM and 10PM, per the rules they have to find something like nine minutes of material that isn't adverts to show in between parts of the programme?