About the reference rate
Reference rates come from Frankfurter, which aggregates central-bank and official reference data. Each currency has its own observation date, shown with the result. They are a benchmark, not the rate your card network, a cash desk, customs or a refund operator will use.
Paying in your own currency
Dynamic currency conversion lets a terminal charge you in your home currency at a rate the provider sets. The markup is the gap between that rate and the reference rate. You can decline and pay in the local currency. Read whether to pay in local or home currency, how card fees work and reference vs card rates.