讲义上说if the trading instrument has a negative MTM value in its lifetime，it will have a favorable impact on netting. If there is a positive MTM valur in the lifetime of the trading instrument，the impact on netting will be less favorable. 不是应该有positive value 和negative value才是有favorable impact吗？只有negative或者只有positive都没有net效果啊。为什么说negative MTM value will have a favorable impact？
