'ipconfig /displaydns' display over 200 DNS unrecognized, should we worry

We are having a problem with a connection and came upon recommended task where we were instructed to run the line "ipconfig /displaydns".   This displayed a series of sites unrecognized to us.

The result showed over 200 DNS and with the list actual sites and IPs.  The sites are in line "Record Name . . . . . :" and "CNAME Record  . . . . : ", the IPs are in line "A (Host) Record . . . :".

For example:

    in.greta.io
    ----------------------------------------
    Record Name . . . . . : in.greta.io
    Record Type . . . . . : 1
    Time To Live  . . . . : 41482
    Data Length . . . . . : 4
    Section . . . . . . . : Answer
    A (Host) Record . . . : 35.186.212.13

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and

    p2-eiiarhhxducde-vnxdzw56kwg3gh6t-299593-i1.stbcast3-stb.metric.gstatic.com
    ----------------------------------------
    Record Name . . . . . : p2-eiiarhhxducde-vnxdzw56kwg3gh6t-299593-i1.stbcast3-stb.metric.gstatic.com
    Record Type . . . . . : 1
    Time To Live  . . . . : 79151
    Data Length . . . . . : 4
    Section . . . . . . . : Answer
    A (Host) Record . . . : 216.239.32.62

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So we wanted to know,

• what is causing this?

• should we worry?

• what should we do?