There is some subjectivity as you could have a delinquent loan still paying and not yet a "loss", as in a Ch. 13 fully secured.
It has been years since I worked with classification requirements and even that was OCC, not FDIC.
Short of direct guidance cited here, and because this policy has such an impact on safety and soundness issues, ALLL, etc., you should discuss the objectives with your regulators and ensure they agree with your methodology.
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AndyZ CRCM
My opinions are not necessarily my employers.
R+R-R=R+R
Rules and Regs minus Relationships equals Resentment and Rebellion. John Maxwell