9F6B

Track 2 Data is Kernel 2's own name for essentially the same chip-carried, sentinel-and-LRC-stripped copy of magnetic-stripe track 2 that the core specification calls Track 2 Equivalent Data (57) - the two tags exist because Kernel 2, defined separately in EMV Contactless Book C-2, specifies its own tag for the concept rather than always reusing 57 directly, even though the underlying data, per ISO/IEC 7813, is the same category of information: PAN, expiry, service code and discretionary data. It's related to both 57 and to the PAN (5A) it embeds, and a terminal implementer working across both contact (which uses 57) and Kernel 2 contactless (which may use 9F6B) needs to recognise the two as functionally equivalent rather than assuming a card that supplies one but not the other is missing data. A cross-check between 9F6B and 5A's own embedded PAN is exactly the kind of consistency check worth running whenever the two are both present and appear to disagree. See EMV Contactless Book C-2.