Applying security errata when host is subscribed to a certain release level

I have a few servers that are set at a certain release level because of application certification.

subscription-manager release --show
Release: 6.4

How do I apply security updates via yum. According to the portal, I have a bunch of security errata that are ready to be applied but when I apply them via yum, it says there are no packages marked for update.

yum update --security
Loaded plugins: product-id, security, subscription-manager
This system is receiving updates from Red Hat Subscription Management.
rhel-6-server-eus-rpms | 3.5 kB 00:00
rhel-6-server-rpms | 3.5 kB 00:00
rhel-server-dts-6-rpms | 3.1 kB 00:00
rhel-server-dts2-6-rpms | 2.8 kB 00:00
Setting up Update Process
No Packages marked for Update

Does this mean that the errata listed in the Portal do not apply to the packages installed on the server at Release level 6.4 ?

Thanks for your help!
Leszek