Recomputes the annual percentage yield earned for a periodic statement from the interest actually earned, the average daily balance and the actual days in the period, all figures you declare, then diffs the recomputed yield against the disclosed figure within a declared accuracy band. Returns MATCHES, DIVERGES with the exact difference, or INDETERMINATE when there is nothing to diff against. An independent recompute-and-receipt over your own declared inputs, not an audit of your core, and not a claim about what it should have disclosed.