To enable registration of quantity when coding, check the Quantity box.
If you have activated a quantity accounting for a bank account, then the incoming and outgoing payments made in a foreign currency will be coded with the foreign amount in the Quantity field. The quantity amount (for example the EUR amount) is then displayed in parallel with the system currency's amount in the accounting. The purpose is to offer the option to "check off" the foreign currency account in the general ledger.