MB maint manual indicates that on a cold start-up, the fluid should be 10mm below the lower line(cold measurement). Once fully warmed up(15-20 miles of driving), the line should be at the top mark.

I've heard it said here and on other sites that the most accurate measurement is taken when warm. I'm not a professional tech., but from my experience, I see the same whether the measuremnt is taken cold or warm. If I measure cold and it's 10mm below the cold line, it will also be right on the upper line(hot measurement) after 15-20 miles of driving.

I suppose yours could be slightly over-filled. I recently paid to have some work done and after picking up the car I discovered the tech had over-filled the transmission. The fluid was a good inch to inch and a half above the full line for a hot measurement. I didn't notice any difference in shift quality, but I did immediately remove the excess by draining some from the transmission pan. In my case that involved the removal of a drain plug accessed with a 5mm allen head wrench.