Template not working as expected

I have made a O2M relationship for showing the history of a cafe.

I want the list to show what I have in the Display Template, but it does not work.
The raw template: ({{Startjaar}} - {{Eindjaar}}) {{Eigenaar}}

I have to click on “1 Item” to reveal whats in it.

Maybe there is something I look over?

Thanks for advice.
Kind Regards,
Wannes