Float will use the base currency from your accounting platform as the base currency for the cash flow. If you have any bank accounts in an alternate currency these are converted and displayed in Float using the base currency.

Similarly, any invoices or bills in a different currency will automatically be converted, ensuring that the cash flow is always displayed in a single currency. 

Clicking into an alternate currency invoice/bill/transaction will display the original currency data, along with the exchange rate used for conversion.