Some weedy detail, for those interested. This is the notice of the proposed rule change (NOPR) for the 6.67 number.

https://www.federalregister.gov/documents/2023/04/11/2023-06...

Also, I think this article from 2019 really adds some missing details, like how the carbon credit exchange works.

https://thehustle.co/09042019-carbon-emissions-credits/