Deceiving boards makes consumers buy thinking they getting it cheaper when they not!!

I visited the Woolworths Matlosana Mall branch 10th Aug '19 and they were having an extra 20% off the quality sale products applicable to all the WMembers. There were 2 boards all over the store and on the racks that had the sale items: 1. Red board - Quality Sale Up To 50% while stocks last 2. White board- Today Only Extra 20% Off Sale Items WMembers Only I ended up buying alot off clothing items. At the till, the cashier doesn't give me the extra 20% off the sleepwear I took. I enquired and he called the manager. The manager tells me that it excluded sleepwear and accessories. I then tell the manager that the board states "20 % off sale items", theres no fine print saying including / limited to womens fashion only NOR excluding sleepwear and accessories. He agreed yet wasnt willing to rectify the mistake. I personally think he should've given me the 20% off and then changed the boards or add an additional board to explain what's included or excluded.