I have gigabit fiber through AT&T. So do my parents 30 miles away. I get a 0/10 from the test-ipv6.com site I logged into my parents network and they get a 1

I have gigabit fiber through AT&T. So do my parents 30 miles away. I get a 0/10 from the test-ipv6.com site I logged into my parents network and they get a 10/10 As I said we live 30 miles away and we both got fiber 2 years ago.