New setting in the NIS 2009 Smart Firewall?

I noticed in the NIS 2009 smart firewall advanced settings there is a new entry that says

 

Automatic Learn IPV6NAT Traversal Traffic

 

What does this  mean and should I have it on or off? It is off now

when I click on the question mark beside it. it shows the advanced settings but does not say anything about Automatic Learn IPV6NAT Traversal Traffic