How do I compare different product origins, and what are the assumptions made for them?

I want to compare "new" materials to "existing" materials. For now, I just made a duplicate of the version, and changed the materials from "new" to "existing", which shows massive reduction in emissions. I can't find any information about the assumptions behind the reduction, what has changed between the versions? And what would be the change for "reused"? Also, it would be great to include product origins in the bulk edit function.