public function addDiscount($value)
    {
        $this->data->amount->subtotals->discount -= $this->convertAmount($value);

        return $this;
    }
public function addDiscount($value)
    {
        $this->data->amount->subtotals->discount -= $this->convertAmount($value);

        return $this;
    }
public function addDiscount ( $ value ) { $ this -> data -> amount -> subtotals -> discount -= $ this -> convertAmount ( $ value ) ; return $ this ; }
Add a value discount

@param  float  $value
@return $this
Add a value discount