Linnworks discount code

I have discounts/coupon codes on my woocommerce website and currently the invoices printed on linnworks only show the discount amount and not the the actual discount code used i.e. firstorder.
The discount/coupon code information is being transferred when you view transaction XML but I don't know how to get it to show near on instead of the total.
Is this something you know how to do and if so how long does it take and cost.
Thank you
Amanda