All currency rates are entered from the Lead Currency to the Included Currency for a given Currency Version. Cross rate between Included Currencies is calculated using the Leading Currency.
...
Enter the Closing and Average exchange rates in the Enter Currency Rate widget. All currency rates are entered from the Lead Currency to the Included Currency. Cross rate between Included Currencies is calculated.
...
The Closing Exchange rates is used for Balance Sheet accounts. The Average exchange rates are used for Profit and Loss Accounts.
Changing the Trend Graph
The trend graph can be changed by click on the currency in the Enter Currency Rate widget.
Some Company and Account combination have specific exchange rates. Specific exchange rates are used in preference to the default exchange rate.
Cross Rates
Select the Cross Rates tab.
...
Setting a specific exchange rate for a Company and Account combination
Select the Specific Rates tab. In the filter bar select the Company and Account that the specific rate is to be applied. Enter the currency rates from the leading currency into the Enter Currency Rates widget.
...