Filter the payment statuses that should be considered approved before decrementing inventory. If the payment status is NULL, it will always be considered approved.
add_filter( 'gpi_approved_payment_statuses', 'my_custom_function' );
An array of valid payment statuses. Defaults to
[ 'Approved', 'Paid', 'Active', 'Completed' ]
This filter is available since Gravity Forms Inventory 1.0-beta-3.21.