Bad attitude from the Manager

Visited Clicks in Walmer Park Port Elizabeth to buy baby clothes that were marked 30% off. Right after paying I noticed on the till slip the items were not marked down, I reported to the manager on duty he went to check on the promotion he came back to tell me the items are already marked down. I told him there's no indication of that cause normally when you pay on any promotion it does show on the slip the items are marked. There should be an indication that i got a 30% discount and then he just said then not on these items. I wasn't expecting the bad attitude from him and he also told me he won't mark down the items further, which I didn't even mention to him because I was still trying to understand why there's no indication on the slip