All Magnifi transactions are based in US Dollars. Magnifi call earnings deposited to an Provider's Stripe Balance are transferred in the Provider's native currency, as selected during Stripe account setup.
Similarly, any refunds issued to Callers on behalf of a Provider are refunded to the Caller in USD, but deducted from the Provider's Stripe Balance in the Provider's native currency.
As per the Calculating foreign exchange rates section of Stripe's Docs, exchange rates used for conversion vary and usually include a spread charged by financial institutions (e.g. approximately 2% for CAD/USD conversion).