The “40% korting in het weekend”, if it is mentioned below Treinreizen, is what you have to pay for journeys you made during weekends with a season ticket that entitles you to discount during the weekends.

Correctiontarieven, or in English: correction fees, are amounts you have to pay if you did something wrong, e.g. forgetting to check in or out. See this page. This might happen by accident if you check in or out at a pole or gate of the wrong transport company, e.g. Arriva instead of NS. You can go through your travel history to see if this happened.

In any case, if you feel your invoice is incorrect, then you should contact customer service directly to have this corrected. Usually, this is most easily done by phone, as they are available 24/7 at 030-751 51 55. You may also contact them by chat (click the link Chat with NS on this page) or by sending a message on Twitter or Facebook.

Before you go foning, check yourself, in travelhistory. This is NOT possible in app, you have to log in via site. 40 eur is a double '’forget to check in/out'’ maybe this comes from check in at NS and check out at another company-this is 1 missed checked OUT (for NS) and 1 missed check-IN-for the nr. 2, makes 2x 20 eur. 40.02 is highly unlikely though.

Missed checkOUTs can be adjusted via again the travelhistory, but a missed checkIN not. IF you make to many of such forgetful checks, in the end your card can even be terminated!

Yes, I am quite aware that this dutch system is a nightmare for other-esp. foreigners, but we expect that uni-students have enough brains to finally understand and live to it. In doubt-ask a well-versed dutch student to help out how it all works! (I have indeed experience with chipcard systems like HongKong Octopus and Singy SMaRT, for the rest just an ordinary dutch traveller).