Example
The company currency is USD (United States dollars). You make an entry in CAD (Canadian dollars) on a ledger account, but the balance on the account is calculated in USD. The CAD amount is converted using the exchange rate for CAD that applies to the current date, as set up in the form.
If at a later date the exchange rate changes, and you want the balance on the account updated to reflect the new exchange rate, you can select this check box and run the periodic job. The job updates the balance of the account using the current exchange rate to calculate the value of the CAD transaction.