You know the little bumbs that are on the edge of the screw holes? What are you those for? Is it normal for there to be scratches on the bumps after screwing, or does that mean that the screw is too tight?
More aboutmotherboard screw holes
To keep the screw in place and to avoid damaging the board when tightening the screw. You don't have to use too much force when thightening them, but scratches might occur.