Order Discount via Line Item Subtraction

{ "rules__5_off_orders_over_90" : {
    "LABEL" : "$5 off Orders over $90",
    "PLUGIN" : "reaction rule",
    "REQUIRES" : [
      "commerce_payment",
      "rules",
      "commerce_line_item",
      "commerce_product_reference"
    ],
    "ON" : [ "commerce_product_calculate_sell_price" ],
    "IF" : [
      { "commerce_payment_order_balance_comparison" : {
          "commerce_order" : [ "site:current-cart-order" ],
          "operator" : "\u003E=",
          "value" : "9000"
        }
      }
    ],
    "DO" : [
      { "variable_add" : {
          "USING" : { "type" : "integer", "value" : "0" },
          "PROVIDE" : { "variable_added" : { "numproducts" : "Number of Products" } }
        }
      },
      { "LOOP" : {
          "USING" : { "list" : [ "site:current-cart-order:commerce-line-items" ] },
          "ITEM" : { "list_item" : "Current list item" },
          "DO" : [
            { "data_calc" : {
                "USING" : {
                  "input_1" : [ "numproducts" ],
                  "op" : "+",
                  "input_2" : [ "list-item:quantity" ]
                },
                "PROVIDE" : { "result" : { "result" : "Calculation result" } }
              }
            },
            { "data_convert" : {
                "USING" : { "type" : "integer", "value" : [ "result" ] },
                "PROVIDE" : { "conversion_result" : { "conversion_result" : "Conversion result" } }
              }
            },
            { "data_set" : { "data" : [ "numproducts" ], "value" : [ "conversion-result" ] } }
          ]
        }
      },
      { "variable_add" : {
          "USING" : { "type" : "integer", "value" : "5" },
          "PROVIDE" : { "variable_added" : { "discounttotal" : "Total Discount" } }
        }
      },
      { "data_calc" : {
          "USING" : {
            "input_1" : [ "discounttotal" ],
            "op" : "\/",
            "input_2" : [ "numproducts" ]
          },
          "PROVIDE" : { "result" : { "result" : "Single discount Line Item" } }
        }
      },
      { "data_calc" : {
          "USING" : { "input_1" : [ "result" ], "op" : "*", "input_2" : "100" },
          "PROVIDE" : { "result" : { "curreny_safe" : "curreny_safe" } }
        }
      },
      { "commerce_line_item_unit_price_subtract" : {
          "commerce_line_item" : [ "commerce_line_item" ],
          "amount" : [ "curreny-safe" ],
          "component_name" : "discount",
          "round_mode" : "1"
        }
      }
    ]
  }
}