factuur

The check-in at Amsterdam Sloterdijk at 17:59 was during peak hours, so full fare. You checked in and out again at Duivendrecht, but since the first check-in was during peak hours the entire journey is still full fare. Only if there is more than 35 minutes between the check-out and new check-in it will become two separate journey's and the second journey is against off-peak rate. 

For more info about this see https://www.ns.nl/en/travel-information/traveling-with-the-ov-chipkaart/frequently-asked-questions.html

The first check-in determines the rate. How does that work?

The first check-in determines the rate for your entire journey. Therefore, if you check in during off-peak hours, this rate continues to apply, even if you make a transfer during rush hour. Checking out and in during your journey to buy a sandwich does not affect the price of your journey. You must check in for the rest of your journey within 35 minutes. If you do not, your second check-in will determine the fare for the rest of your journey. Therefore, if you continue your journey during rush hour, you will pay the full fare.

Please note: this also works in reverse. If your first check-in was during rush hour, this rate continues to apply.