You've found the 'voucher' for the Rainy Day Pack Original Chilli Relish X 4 bundle.
It's added to your basket automatically and activates the discount when you buy the bundle. No point in adding the voucher to your basket on its own, so head over to the page for this bundle and take a look there!
Queries about discounts? Please see the Discounts & Offers page for some helpful tips.