It happens in domain mode when different hosts have different patches applied.

from the BZ:
In EAP 6.4.0, after patching 6.4.6 on slave host and restart it successfully.
Patch Management shows the "Latest Applied Patch" is "jboss-eap-6.4.5.CP", although the "jboss-eap-6.4.6.CP" was list in "Recent Patch History" below.

After patching on Master host and restart it successfully, the "Latest Applied Patch" of slave host is "n/a".