If you have set the option to periodically check the proxies it will periodically pop up. This is done to ensure that the private proxies have not gone down. If you are using thousands of proxies there is a strongly probability that they are not private proxies and will require regular checking to prevent running with bad proxies.
Rather than running with public proxies unfiltered I would strongly advise to run with either private proxies or get a software to constantly check public proxies for you to ensure you only ever have a smaller list of more reliable public proxies.