We pick b.root-servers.net, one of the 13 root servers (1), and ask it about avonturenparkhellendoorn.com and learn that com is delegated to 13 name servers (2), so we ask f.gtld-servers.net where we learn that avonturenparkhellendoorn.com is delegated to three name servers, including ns1.leaseweb.nl (3), so we ask that one and get the following answer:
All of the several thousand of domains that use the primary name server ns0.leaseweb.nl use name server group 1 (example: helldorfer.nl, glazenburg.nl and antispy.nl ). Worth noting is that half of the domains that use name server group 1 use the primary name server ns0.leaseweb.nl.
The three name servers ns4.leaseweb.net, ns1.leaseweb.nl and ns5.leaseweb.nl together
There are several thousand of domains that use name server group 1.