This configuration looks like it is intended as the ntp server for your organization. It obtains the time from external sources. And it is will to distribute the time to other boxes. So there might be other boxes that use this box as their ntp server. Or maybe this box is the only system in your organization.
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10
This is a NOT great idea in your situation. You have specified, that in the special case where no other servers can be contacted, to use the local clock as if it were a server. Well, you have also stated that your local clock is off by 15 minutes. Any other boxes that get ntp through this box will try to sync to this box's local clock. If you remove those lines, if this box can't contact a server, you have no ntp service. Everyone just uses their local clocks. If this box does not serve others, there is no harm, but I still would not do it. This should be done only on systems with great internals clocks.
driftfile /etc/ntp/drift
You are using a driftfile. That is good.
server 132.249.20.60 # billthecat.sdsc.edu
server 204.152.184.72 # clock.isc.org
I did not find the first site on the lists. The second site is a stratum 1. I would just use the second entry. If you use multiple servers, you need at least 3. Two servers does not work very well.
Read the
NTP FAQ, especially the part about NTP in real life.