Question: Problem of double unit conversion in a parameter

I would like to define all the geometry parameters in a multibody model in MapleSim in mm.

Consequently, i define the mm unit for a parameter in 3 places :
1)  in the Parameters area of the subsystem 

2) in the Tab Inspector of the subsystem

3) in the Tab Inspector of the rigid body frame of the subsystem

The problem is that I receive the warning "Possible double conversion unit on a parameter" and the dimension seems to be as 10^-3 *mm soit too much reduced.

I see that in some examples of the library of Maplesim the parameters of the parameters area of a subsystem are defined as real and consequently, it doesn't cause this kind of problem.

However, how can I do if I want to define my parameters in the parameters area of a subsystem as a position in mm ?

Thanks a lot for your help