The rule of thumb is not to put more in than you took out. Measure what you drain before filling.
I changed the oil of my 300SD yesterday. The engine capacity is 8 quarts but since 8 quarts didn't come out, for whatever reason, I did not pour 8 quarts.
The other thing is that many MB gurus say to keep the oil level halfway between the add and full marks on the dipstick. That means a quart shy of capacity for my 617. Probably something close to that for your 616.