This strategy involves initiating a larger position in either direction to the original one after experiencing a loss or while the initial position remains open.
E.g. If you open 2 lot BUY on EURUSD. Then you open a 4 lot SELL (or BUY) on EURUSD.
This is Martingale which is not allowed.
Hedging #
Where hedging is up to or the same size as the original position.
If you open a 2 lot BUY on EURUSD, then up to 2 lot SELL on EURUSD, this is entirely allowed, hedging is a great way for traders to manage risk.