The commission for a round-lot is charged at USD 7. But when USD is not the base currency, it can be confusing, so please see the example below:
Example: 1-lot EURUSD trade at the exchange rate of 1.3200 will be subject to a commission of USD 9.24, as the base currency is not USD.
EUR 7 x 1.32 = USD 9.24
Bear in mind that the commission is always USD 7 per 1-lot of USD, regardless of the instrument you trade. If USD is not the base currency, you will have to use the exchange rate to USD.