Problem with numbering in TOC

I don't know how I got this in my TOC:

The problem is that I get an extra "1" before the word "Inhoud" and also before "1     Foundation    5" and other chapters.

I don't know how to remove this "1".  I understand where the other numbers are coming from.

I thought maybe the style of Foundation is based on another style which has also a numbering. But that was not the case.