Well I finally found out why my racquet had that much difference of weight.
there was about 4 g (0.141oz)of foam in to the handle
I only buy used racquet and I guess the previous owner forgot to tell me about it.
Now the racquets weights 11.3 oz as the spec says.
However, this could be a god idea for all the people who would like to ad some weight in to the handle without applying silicone which is much harder to remove.
It was that kind of yellow foam that you would find in chairs or sofa.