It is an option in MT5 platform that allows a trader to close two hedged positions by sending one order.

Example: there are two open positions on the trading account. 1 lot Buy EURUSD and 2 lots Sell EURUSD. By clicking on Close by 1 lot Buy => there will be 1 lot Sell EURUSD left on the account. One click has closed both 1 lot Buy EURUSD and 1 lot Sell EURUSD. This feature is not provided.