Unknown Service Detection Banner Retrieval
This entry from Security Metrics indicates that the scan can see a TCP SYN banner for an unknown protocol.
The specified service is not known to have a vulnerability.
By simply telnetting to a port, header information may be offered by the specific protocol to which you connect. This is not indicative of a particular risk or vulnerability.
No action is specifically required.
In this case, you may know more about the protocol running on that port than Security Metrics does. If this is not a public service, consider removing the general incoming firewall rule and replacing it with a targeted custom rule which allows only those hosts which require the server.
This may not be tenable so a refutation of the risk may be all that is required.