update the invoice number calculation

app/services/order_invoice_generator.rb

@@ -9,7 +9,7 @@ def generate_or_update_latest_invoice
     if comparator.can_generate_new_invoice?
       order.invoices.create!(
         date: Time.zone.today,
-        number: order.invoices.count + 1,
+        number: total_invoices_created_by_distributor + 1,
         data: invoice_data
       )
     elsif comparator.can_update_latest_invoice?
@@ -31,4 +31,8 @@ def comparator
   def invoice_data
     @invoice_data ||= InvoiceDataGenerator.new(order).generate
   end
+
+  def total_invoices_created_by_distributor
+    Invoice.joins(:order).where(order: { distributor: order.distributor }).count
+  end
 end