I won't get into the exact weights, because I don't have the underlying dataset and it's not my job. But the basics of the formula are pretty straightforward.
We know that a single is slightly more valuable than a walk (since a single can advance a runner 2-bases). We also know a double is more valuable than a single, etc etc etc. We also know that stealing 3rd base is more valuable than stealing 2nd. All of that is intuitive. So can - instead of times reached base - there be a metric which is more useful? Now, total bases is okay - but that ALSO is not good enough. Like, two singles is more valuable than a double. So Runs Created is meant to take all of these positive outcomes and combine them based on how important they are to scoring runs.
Where stuff like this is useful is just to give a way to relate the offensive value of prime Wade Boggs vs the offensive value of prime Manny.