What does ‘under the completely sufficient imputed righteousness’ mean?

EPISODE #72: Ted asks about Dad’s long-used email signature and what it means. Rod talks about the history of how the Catholic church spoke of justification in the 16th century, and what Luther and Melanchthon began to focus on at the beginning of the Reformation—imputed righteousness—and how it’s the only righteousness that saves, and that it is enough for us sinners.