MPM is Maximum Permitted Mileage, which means the routing allowed from SFO to ROM allows you to fly a distance of 7507 miles (in one direction). This includes the distance of all connections.

You can exceed this MPM by up to 25% by paying a fare that is proportionally higher in 5% increments. If you exceed MPM by 4%, you pay 5% extra on the base fare (in that direction). If you exceed MPM by 6%, you pay 10% extra on the base fare.

Ticketed Point Deduction means when you connect through the listed cities, you deduct the deduction from the MPM calculation.

For example, a route from SFO-MIA-LHR-FCO would be 7908 miles, which is over MPM so you'd have to pay 10% extra of the fare. But as there is a deduction of 550 miles for going via MIA, the distance becomes 7358, which is under MPM. So that means the 10% extra does not apply.

Keep in mind that all the miles used here is strictly for fare calculation purposes and not necessarily what one gets in the FF program.