That link doesn't support your claim:

>> Your bank may or may not use the rate indicated by this calculator to bill you

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(As a side note: the fine print follows up with this:

>> If your transaction is converted by the merchant or ATM operator, the exchange rate indicated by this calculator will not apply.

Don't ever let a merchant or ATM do foreign currency conversion for you. They charge astronomically high fees without exception. Pay in the foreign currency and let your card do the conversion.)