Looking to manage some GBP cash using a box spread, and working out the implied discount. Never traded Z index options on IBKR before and can't seem to see how much the FOP commission is on its website. Footnote 5 says GBP index option Cost+ commissions will start at 0.60, so how much is it per option? Also, it says that commission is charged again at expiration/assignment, so I should use commission per leg x 4 x 2.