As Randy said, for your E320 it's specifed to read the dipstick about two minutes after shutdown - about the time it takes you for the service guy to check at a full service station.

Also, Mercedes reduced the specified oil charge from 7-1/2 liters to 7 liters for your E320 M104. This would be around the half-way mark on the dipstick. It has something to do about the original capacity listed in your owners manual as being too hard on the seals. So don't even think about putting in excess oil in the crankcase.