hmm, doesn't seem to match my numbers over here. If I try to order up a vertical put spread on /ZNZ19 for DEC 19 - 130.5/130 my maximum loss is 265.63, and my buying power effect is -108.00.
Come to think of it this might be SPAN margining taking effect. I'm used to trading equity options where generally speaking maximum loss and buying power effect tend to be closer to equal.
