This happened in Whole Foods a month ago. I needed a refund and they said 6776 is the last four of my credit card... and expiration date were also different from credit card set up with Apple Pay, they finally resolve it but it was a big headache.
Fast forward, last night I finally signed up with Uber. They had a use applepay option, which I did, and in profile, it says, Mastercard, last four digits --which again, are not, numbers not on my MC card, different expiration date from card. What is this? Does Apple know how confusing/ odd this is?