9F6A

Unpredictable Number (Numeric) is the mag-stripe-mode contactless equivalent of the terminal's core Unpredictable Number (9F37, covered earlier): the same random-value-per-transaction concept, but expressed as numeric digits rather than raw binary, since it feeds directly into the CVC3 computation (9F60, covered earlier) that mag-stripe-mode Kernel 2 transactions depend on for replay resistance. It's related to both 9F37 and 9F60, and exists as a separate tag from 9F37 specifically because the numeric encoding this particular computation needs differs from the binary encoding the core cryptogram flow uses - the same underlying security property, freshness, unpredictability, one value per transaction, implemented via two different tags because two different downstream computations need the value in two different formats. A terminal that reuses a 9F37 value directly as 9F6A without the correct numeric re-encoding will feed CVC3 a malformed input, weakening the mag-stripe-mode protection this field exists to provide. See EMV Contactless Book C-2.