I forgot to check in at Schiphol on 30 March around 22:30, the check out station is Weesp. I was charged for 12 euro. I made a declaration online, it showed that I will get 6.1 euro back, which means I paid this trip for 5.9 euro. This is not correct because I have flex dal voordel, so it should be 40% of 5.9, which is 3.54 euro. Therefore the refund should be 8.46 instead of 6.1 euro. Please let me if my calculation is correct. If so, would NS refund the rest? Thank you!