You need to assign to Purchase event a dynamic value:
fbq('track', 'Purchase', { value: final_price_without_currency, // This is from Facebook's docu. Not recommended currency: 'USD' }); // You should look into your Checkout file and find the Value WithOUT currency. In my case (PS 1.6.0.9) : fbq('track', 'Purchase', { value: ecomm_totalvalue_tax_exc, currency: 'SEK' }); // See the attachment to have an image of how it should look like your "Thank you"/ "Order Success" HTML page.