Protit from derivative

I have one doubt. sum of positive and negative diffrence of future trades is the turnover. Shouldn't we subtract twice the amount of losses to correctly arrive at GP, because while originally calculating the turnover, we had removed the minus sign on losses. Example: Trade 1: -5,000 Trade 2: +10,000 Trade 3: -2,000 Thus turnover = 17,000. GP is really 3,000. To arrive at GP correctly, we need to calculate: 17,000 - 2*(5,000+2,000).