Dear Materials studio community

I am new on molecular dynamics and I have a problem with assigning negative charge to my organic molecule.

I am used to study the interaction of negative charge collectors to the mineral surface. So what I do is to draw the molecule structure and then I assign -1 charge through modify/charges/edit/set total charge to -1e. Then I go to discover setup and I calculate the forcefield energy. After convergence, I never have -1 charge for my molecules, it is like it does not consider that I have already assigned -1 to my molecule and I have close to zero charge for my molecule. I appreciate if someone let me know where is my error.