I think it is a difference in the processor that Walmart uses for the specific transaction. Walmart typically uses ChaseNet to process payments made using a Chase card, but it uses another network for other cards, including other VISA issuers, and it has the option to route Chase transactions through the primary network.
In 2016, Walmart announced a pact with JPMorgan Chase ....
The processing deal, which expands on the companies' earlier relationship for handling Walmart’s e-commerce transactions, diverts Chase card payments at more than 5,000 Walmart and Sam’s Club stores through ChaseNet, a closed-loop system designed to slash costs for merchants.
Chase accomplishes this by acting as the acquirer, network and issuer for transactions where both the cardholder and the merchant are Chase clients. And from the perspective of Walmart, this deal hands it a long-desired holy grail: less expensive Visa transactions.
“We will still have a relationship with Visa for non-Chase transactions,” but the deal with Chase "will bring much-needed competition to the payments markets," said Randy Hargrove, a Walmart spokesman, at the time of the announcement....The deal with Chase gives Walmart significant new leverage in how it handles Visa transactions. “Walmart will have the ability to selectively route transactions based on the performance of the payment providers,” Hargrove said.
https://www.americanbanker.com/payme...u-need-to-know