Fixed header discount value

wizard/pos_export_bc_wizard.py

@@ -95,7 +95,7 @@ class PosExportBcWizard(models.TransientModel):
                 invoice = order.pos_reference or order.name
                 
                 subtotal = sum(l.price_subtotal for l in order.lines)
-                discount_order = 0.0 # Standard Odoo doesn't have an order level discount easily isolated from line discounts
+                discount_order = sum(abs(l.price_subtotal) for l in order.lines if l.price_unit < 0)
                 tax = order.amount_tax
                 charge = order.amount_total
                 # In Odoo, payment amount can be negative for change.