Interestingly, the three people say the last digits of their credit card numbers were included in the dump, while the Ashley Madison CTO says they don't keep credit card numbers, full stop.
Having said that, Ashley Madison has approximately zero credibility, so whatever their agents say is open to intense skepticism.
If you work with external payment gateways sometimes you are provided with this information even if the card processing is done directly on the processor page (you only have access to limited information about the card and the transaction)