ACA Override Upload fields question: Delete and Flagged

Is there a guide explaining how to use the ACA Override Upload / ACA Reporting Upload HSDL? (Benefit Administration > Evaluation and Reporting > Person Data Loaders). I have found some guides explaining what this HSDL is used for (overriding ACA fields in the ben table) but not how to fill it out. What process and report flows are available for the US?

Specifically, I am wondering how the Delete column and the Flagged column are used. Also, what should the effective date should be (my org seems to have used Dec 31 in past years).