Foreign money (expenses, settlements, deposits, buyouts, cash in or out) keeps its own amount and currency, and converts to USD for every total and export.
WHICH RATE: each item converts at the exchange rate on its OWN date (the expense date, the show date), not the day it was typed into ATOM and not today. A pound spent on June 26 stays worth what a pound was on June 26, so old totals don't drift when the market moves. Rates are the European Central Bank's daily rates; a weekend or holiday uses the last market day before it.
TODAY'S RATE is used only for money that hasn't happened yet: what a venue still owes, a future show's guarantee, and the Currency Converter.
A RATE YOU SET in Money > Settings > Display & app > Exchange Rates wins for that currency everywhere, on every date.
The Currency Converter on the Money tab is a quick reference (13 currencies).