Increases or decreases an existing position by the specified factor, if the market hits the stop price. See: AdjustPositionOnOpen for a more complete description of the adjustment factor.
Increasing a position size will result in adding units since the contract/share additions will have a different entry date than any of the existing units. Decreasing a position size will remove contracts/shares starting with the last unit on, and working back to the first if necessary.
This function is generally used by a Risk Manager Block to lighten a position to meet certain risk restrictions.