Perk converts expense amounts (i.e., receipts) in foreign currencies to your company currency both to enable matching and to reclaim VAT after export. However, the conversion of transaction amounts is dependent on the bank providing your company cards and may therefore differ slightly from the expense amount.
The currency you want amounts to be exported in can be set by an account admin in Spend settings (Settings > Account > Companies, Spend settings), in Enable company cards for this company.
This allows you to determine if you prefer amounts to be exported in the card currency, transaction currency, company currency, or original expense currency.
Tip: For more information about foreign currencies, see Why do the expense amount and transaction amount differ from each other? and Why do some transactions include the foreign currency charge, whereas other transactions separate it?