I saw a UI vaguely similar to the sites page, but unlike the sites page, I instantly understood this one. It had the two halves of the mapping, but instead of just the delta paths, the full URL and full file path were listed. This made all of the difference! Right off I knew which was which, no guessing or reading. I could copy them into the browser/file system and test them instantly. I could copy in the reverse direction as well.