Pertaining to the material exchange with the Vanguard Quartermaster. Generally you exchange 50 of a specific material for 5 vanguard marks +25 Vanguard Rep + 200 Glimmer. Unfortunately the 5 vanguard marks seems to be tied into the total you can receive for the week from strikes. I didn't see any indication this would happen until wasting a couple of exchanges myself. I'm not sure if this is intentional or a bug.