That's the time in milliseconds when Yappari will try another read from the network socket.

If you change it to a higher value, the GUI should freeze more often in bad connections. If you change it to a lower value, the GUI should response better, but your battery will last a lot less.

It doesn't really has anything to do with the socket timeout, which is 300 seconds (5 minutes).

If you read the code you'll see that no matter what value you set there, it's inside a while loop so it will still try to read until it reads what it needs to read, or until the socket times out and throws an exception.