The instructions on your link right above are a bit different from others I read on this site.
I've run the setup once before. It stuck at 51% for maybe 30 minutes, then quit with an "Error Code 30015-25 (-1610612703) "
I launched the setup again, and it's slowing installing again, up to 30% right now in about 20 minutes.
But, just being proactive, if I have another stuck installation, especially with that error code, what do I do?