steakwizard lower the total amount of max simultaneous connections in the settings of the DL manager. Because of how long your downloads will take, queuing them up will likely fail too.
The idea behind a download manager is that it opens multiple connections for a download file. With SLR, this happens even when you're not using a download manager. Browsers don't always handle this well, and other issues could occur, but it's too much technical stuff to go into.
So in your specific situation, we are trying to limit the simultaneous connections because of reasons in an attempt to make the downloads not fail so easily.