Weight problem in free size optimization

I have a problem with free size optimization.

My weight limit is 35 kg. The optimization runs and converges, results make sense.

When I import the *.fem file in Hypermesh I am checking the weight of the component usint Tools - mass calc. The problem is that I get an higher value (50 kg) of what the constraint is (and in the output file i clearly see that the weight constraint is respected). It is not a question of considering other component in the calculation as I have only one.

I had a look also at the formula student monocoque tutorial and files and I see that if I try to import the file ' 04_freesize_sizing.18.fem' the weight is 57 kg and not 50 as it should be. 

Where am I wrong?