This's for cdn selection. When we try to download from a slow cdn, we can disconnect it fastly and try another one.
In your screenshot, we can also confirm this. You are downloading form some slow servers, which only get about 300KB. After disconnect from them, it will try the other server and your download speed up.
What's more, the script will remember the server stats (https://github.com/armbian/build/blob/master/lib/functions/general/downloads.sh#L62-L63). So in next download, aria2 will choose the fastest server.
