You can buy or sell different amounts of each currency pair — from as low as 0.01 lots to 5 (the maximum position size in the largest account).
To calculate the lot size of your trades, we add up the number of lots that have been opened and closed. For example, if you were to trade four separate 0.5 standard lot trades, that would equal 2 standard lots (0.5 x 4). To reach the 50 standard lot threshold, you could trade 50 standard lots or 500 mini lots (0.1 x 500).
The cumulative number of lots traded is automatically calculated on your dashboard here.