This is because starting from the 21st of January, 2020, Apple Card users will be able to export their monthly transactions. What this means is that you will be able to export all the data from the purchases you’ve made into your own personal finance or budgeting apps, thus allowing you to get a better idea of the things you’ve purchased, when you made them, and how much they cost.
At the moment the only format support is in CSV, but in the future there are plans to support other formats like Open Financial Exchange, but Apple did not provide a timeline as to when that will happen. The export function should already be live and it seems to be a server-side update.
This means that users will not have to do anything on their end, although it could take up to 24 hours before you see the function available, so don’t worry if you don’t see it yet.