"Supplement Required" - Rotterdam to Amsterdam

Hello, tomorrow (Oct. 17, 2023), I will be traveling from Ghent to Amsterdam.  The journey has 3 segments, the last of which is Rotterdam to Amsterdam.  The Eurail site is saying that a supplement is required to board the train, but the information on supplements indicates that the supplement applies to Rotterdam to Schipol Airport.  The Rotterdam to Amsterdam train stops at Schipol, but Schipol is not my destination.  Do I need to pay the supplement and if so can I pay it on board the train?  I thought I read it could be paid on board, but I’m not seeing this when I just checked this route.   Thank you!