Extended Update Support RPMs x86_64 7Server .vs. Extended Update Support RPMs x86_64 7.3

Hello,
We have recently acquire subscriptions for Extended Update Support, and I am trying to understand how to use this. We need to start updating a number of RHEL 7.3 hosts that cannot be upgraded to 7.4. I see separate repos for a number of options under EUS, including a discrete repo for 7.3, 7.4 and one, seeminly general, for 7Server. Which one should I use for my 7.3 hosts, the 7Server, or the 7.3?
Thanks,
-- GV.