Entitlement matrix for RHEL server?

I'm looking for information on how entitlements work on RHEL server systems. I can't seem to find this info on-line. We have a subscription that shows 15/16 on the utilization summary page in the portal. The server I am trying to subscribe is a quad core single socket system. The error I get when I try to manually attach a subscription to that system using that last entitlement is "Subscription 'Red Hat Enterprise Linux Server, Standard (Physical or Virtual Nodes)' must be attached using a quantity evenly divisible by 2". My questions are:

1) Could I have subscribed this system if it was a single socket but DUAL core?
2) Are 2 entitlements ALWAYS needed to subscribe a single socket quad core system?
3) How many entitlements are needed to subscribe a dual socket quad core? Dual socket 8 core? Single socket 8 core? Quad socket quad core, etc..etc..
4) Is there an Entitlement Matrix somewhere I can go to that will show me this info?

Thanks in advance!