The railplanner app doesn't have the correct info. The train number is 9315. Info below from Deutsche Bahn.

Okay but it should be all good to go and okay to add to the journey/pass either way? 

There'll not be a problem on board?

No problem to board as you have a seat reservation for the correct train. 

Adding the journey to your pass should always be done just before boarding the train. You can always add the journey manually, but the train number is not important for the ticket created in your pass.

Thank you! 

This often happens when Thalys runs a train with 2 train sets. They're technically run as 2 separate trains with 2 separate train numbers, here 9315 and 9415. They can even have different fares available (here for a senior):

The train number on the reservation will depend on the train set you're booked in. What a planner will show depends on how it is set up, I suppose.