When parent and child orders are automatically generated by an app in Shopify, be aware that "customer.total_spent" may differ from the actual total amount paid.

The {{ http://customer.total_spent }} variable tag can be used to display the total amount spent by the customer, but if you are using a Shopify app that automatically duplicates orders, the duplicated orders will also be included in the total amount, so there may be a discrepancy with the actual total amount spent.