GTM - SOA and NS record naming convention

I have recently completed a GTM deployment.

 

gtm1.company.com

 

gtm2.company.com

 

When I look at the resource record list... I see my SOA and my NS records showing RDATA of my GTM hostname.

 

This is my question:

 

What is the best practice to naming it?

 

I was thinking gtm1 would be ns1 and gtm2 would be ns2 but when I try to update the zone resource record... it changes both the gtms automatically.

 

Am I missing something?