The Minimum transaction size on STP accounts is 0,01 lot (1000 units of the base currency). If you do not see the exact volume you'd like to trade in a drop-down list in the New Order window, type the volume in the Volume field.
The Maximum transaction size on STP accounts depends on the available liquidity.
The Maximum number of trades on STP accounts is unlimited. You may open as many trades as your margin allows.