Can somone explain this GL_SPEC_OPENING

Can some one explain this firewall rule in GL-INET XE300 - LUCI - FIREWALL in as below screenshot.

also How can i block unwanted sessions and drop all unwanted ports.
also list all session going from router? in more details

This is a china for all GL.iNet defined firewall rules.

If there is nothing defined in the UI, this china is empty.

Hi can you pl tell, where can i view all connections specific to glinet firmware to outside firware like above also like all dns requests, other telementry going from router ? and goodcloud connections? if not enabled?

You need to use data packets analysis tools like wireshark to analyze data.