What does "exchange" on my card transaction statement mean?

If you don’t have enough money for the transaction you’re making in that currency wallet, we’ll take money from the balance you have in your other wallets to complete the transaction. We call this “wallet alignment”. You’ll see that the balance in the currency you are paying in will go into a negative temporarily, this should only show for around an hour. The wallet alignment process will then take place and money will be taken from another wallet, correcting your negative balance. These are the transactions you will see noted as an exchange on your statement.