How does multicurrency work with Split Payment & Deposit?
When the split order is made in the currency other than the currency of the store, the currency conversion fee is charged whether you use automatic exchange rates or set exchange rates manually.
Currency rates are always fluctuating. Whenever there is a time delay in processing payments, there is a possibility that you might lose or gain money because of currency conversions.
Installment payments (and sometimes split payments) mean that the date of order creation and the date of final payment will differ, and this can result in a small pricing discrepancy. For example, if the price is $100 USD, the merchant will receive $99 USD after converting the amount to store currency.
Learn more about how Shopify counts the total captured amount of such orders here. Contact Shopify support team for the questions related to conversion rates.