This value represents the time, in seconds, that is used to establish and keep connections with the sites. If this value is low, you will have a 'Can't connect' message when you launch a heavy remote task.
For instance, let's suppose that a File Integrity task takes 2 minutes to be completed. If we set a value of 30 seconds here, the remote task will be launched but connection with the site will be closed before it finish, so we will get a 'Can't connect' message.
As sites contact back with the Control Center to report tasks result, if Control center is installed in an isolated environment (i.e. your laptop) sites won't be able to reach it. Looking for a way to make a local site accesible through internet I have found a couple of enterprises offering this service: ngrok and pagekite. The first one creates an http (or tcp) socket between your computer and their servers using a simple executable file. This socket can point to any local IP and port. This way there is no need to do port forwarding or using other techniques: just put the socket name in a browser and you get access to your local server.
Putting your ngrok (or other) name in this field all queries will come back to your local installation of control center.