Opaque operations, exchange rates from the supplier.

I paid for the goods using a POS terminal. The rate was 2525 UAH for 60 euros at a rate of 42.42 (according to banks in Ukraine). The app displays an exchange rate of 45.67, which equals 55.28. The Mastercard exchange rate was 42.42. In the end, I was charged 60 euros at an exchange rate of 42, but I couldn't get an explanation from customer support about where they got that rate from.