Confused over Sales Tax - Origin vs Marginal Base


(I posted this in the technical forum but didn’t get any replies so Ithought I’d try here).

Could anyone clear me up on how these two definitions differ ?

Im confused because, for a given tax code, I can set the ‘Tax Calculation Method’ in the origin field to be, say, "Percentage of Net Amount’ but can also set the ‘Marginal Base’ field to, say, ‘Gross Amount per Line’ etc

These two properties seem to overlap to a large extent and potentially conflict.

Thanks in advance for any on this.