Still do not understand where my NTP server is getting its source time from

I got some fantasic help today understanding and making NTP work on our network. I know which DC is the PDC emulator and I think I have all 3 DCs synchronized. My last question deals with where my PDC emulator gets its time from. I no longer see that it synchronizes with time.windows.com or even a tab where I can assign a major internet time server. I was to
run w32tm /monitor and got the following results. How can I confirm that my PDC emulator is syncing with an internet time server? If it is not, how can I configure so it is routinely syncing with a major internet time server?

C:\Windows\system32>w32tm /monitor
P-AD-DC01.PTI.local *** PDC ***[[::1]:123]:
    ICMP: 0ms delay
    NTP: +0.0000000s offset from P-AD-DC01.PTI.local
        RefID: time.nrc.ca [132.246.11.229]
        Stratum: 3
P-AD-DC02.PTI.local[10.3.1.32:123]:
    ICMP: 0ms delay
    NTP: +0.0050158s offset from P-AD-DC01.PTI.local
        RefID: P-AD-DC01.PTI.local [10.3.1.31]
        Stratum: 2
P-AD-DC03.PTI.local[10.3.1.33:123]:
    ICMP: 0ms delay
    NTP: +0.0033576s offset from P-AD-DC01.PTI.local
        RefID: P-AD-DC01.PTI.local [10.3.1.31]
        Stratum: 4

Warning:
Reverse name resolution is best effort. It may not be
correct since RefID field in time packets differs across
NTP implementations and may not be using IP addresses.