Gimmick discount vouchers

Discount vouchers are being handed to Clients after purchase. I received 25% off Castle Light 410ml 'per item'. When I went to redeem this voucher for a case of Castle Light they tell me it is on 'one item', not meaning a case or a six-pack - it is for one can only! Surely one item should be one six pack or one case or even just one beer if that is what I wanted to buy. If I buy a packet of smarties, the discount is for one box, not one smartie. What a gimmick, we are being treated like idiots. Instead of attracting Clients, they have definitely annoyed this one once again.