The need for IPV6 records in DNS

We just took over responsibility for the external DNS and have noticed that
there are IPV6 records in some of the zones. As far as we know (which is
limited) we have no use for IPV6 records in our external DNS and nobody seems
to know the IP address was determined and/or how it was aquiired and whether
they are even valid addresses. As far as we know we only have IPV4
addresses. Can someone clue me in on where these might have come from or how
they were determined?

Thanks,