Verifying fields consistency
Your form contains the vads_amount field. This field corresponds to the total amount of the order.
To make sure your form is valid, the payment platform verifies the entered value.
The equation used is as follows:
Sum ( vads_product_qty(N) x vads_product_amount(N) ) + vads_shipping_amount + vads_tax_amount + vads_insurance_amount = vads_amount
If the value entered in the vads_amount field is incorrect, your payment form is rejected due to invalid amount.