Old Domain Controllers appearing as trust anchors on DNS

I have a Windows 2008 R2 system. I see some old domain controllers appear when I run the command below:
dnscmd /zoneprint /trustanchors

I did attempt to remove those records by running the command below:
dnscmd /recorddelete TrustAnchors dcx.test.com NS

It says it removes the record successfully but when running the zoneprint command, the records still show. I flushed DNS and cleared cache.

I am not too familiar with this level of detail within DNS, so pardon my ignorance. But could someone explain to me what this implies and if I should be concerned at all?

Thanks!