Supervisor should be send on basic maths/interpersonal skills courses

[Woolworths Foods Vanderbijlpark Riverside Centre] Buying 3 bottles of wine with 50% off, led to some frustration trying to make supervisor and manager to understand some basics sums. Arriving at the cash register, I was told that it is actually 25% off when buying 3 wines (Hartenberg Shiraz @ R150 each), but sticker had it as 50% and not 25%. Some debates also with supervisor (I think, Mbali) and she started to make some sums and entries on cash regsiter - still getting to R337,48 (the amount when only 25% had been deducted. She kept on confirming that, that is the amount as she entered the additional 25%, which was incorrect. After also involving the manager and further discussions, he conceded that 50% of 3 bottles was R225 (which was that correct amount). I wasted some 20 minutes at the cash register just in trying them to understand, with especially the supervisor really lacking insight into basic maths (and customer service/interaction). I would recommend she attend some personal interaction and basic maths course to ensure avoidance of this again in future. I was so frustrated, with queues of people staring on what the reason was for the hold-up in service (Very, very long queue). I will rather go to another Woolies and also relay this experience within my personal network. Woolies, you really can do better!