The Trading ToolBar is composed of 4 buttons. Each button is defining a different level of risk and it automatically adjust the trading size in respect of the chosen risk parameter.
You can adjust the target, stop and entry levels but your risk will always stays constant.
As soon as the risk button is clicked you move your mouse first at your stop level and second at your entry level. That's it no need to bother about how much size to put on which is a big advantage specially when the market is moving fast.
Obviously you can change your levels anytime and the trading size will adjust automatically.