I rethought it and came back with guess number two and deleted the first surmise I had posted. This time I think maybe this is the way it should be done. As I said to start with, I wasn't able to find an explanation on the internet that showed in photos how to do it right clearly enough for me to understand. So, after stumbling around in the dark for a while I think I am on the right track. Or.... you could put strap on so that the buckle puts the tab end of the strap on the outside of the web sling which would be yet again another theory.
I like the tag end inside the sling a little better I think, although outside may be more likely correct. Here is my inside the strap tag theory.