HiCustomer how many miles are on your Mercedes?
Ok, the service F is simply an indication of the amount of time that will be required to perform the services that are due. The F service is allowing 6 hours for completion which is alot for only 26,000 miles. To find out which services are being called for you will need to access them from the service menu on the instrument cluster. I can explain how to access the service menu to see what is due if you'd like. Let me know.