As the service letters get deeper into the alphabet, the more labor is expected to complete all the operations the service minder determines are needed. There are check lists and those list have the service items listed with a general mileage and time that a service item is deemed to be needed. Like for coolant it might say 10 years or 150,000 miles. So a "g" service means that if all the check list items are actually needed at the time of service, you can expect to pay for about 6-8 hours of labor. After the "g" service is done you can expect your service minder to display an "a" or "b" service due in 10-13kmiles.