Nr. always 1

I just tried out this Plugin.
I set up a simple List of participants,
just the Name, free field, Previous registrations and Nr.

When I enter entries to the list they all get the Nr. 1
Name Nr. Boot
Robert 1 Elbe
Mary 1 Donau
Bob 1 Oder

Shouldn’t the number not 1, 2 and 3?

https://www.ads-software.com/extend/plugins/list-of-participants/