Duty-cycle is often called On-Off ratio but if it were called Off-On ratio it would be the inverse.
Duty-cycle point of reference can be changed on most good meters (including those flukes). If the duty-cycle on is 70% then the duty-cycle off is 30%. You have to decide which period you are talking about.
As a point of reference your car should have a 70% duty cycle with the key on engine off. Verify and correct your point of reference on this number. (If your car is a Ca car it will be 85% instead of 70%)
Bosch Master, ASE Master, L1
33 years MB technician