[Terminology] Carbon Delta and Carbon Counterfactual

[TaylorPrewitt]

There has been a few different interpretations of this terminology, so I wanted to propose a couple definitions to get everyone on the same page.

Carbon delta: The difference in emissions between a carbon aware and an unaware action.
Carbon counterfactual: The carbon delta had the carbon aware action been different.

[atg-abhishek]

I believe this is now included in the SCI spec @TaylorPrewitt - please let me know if you concur and we can close this discussions. Thanks!