Training needed

On the 24 September 2018, I purchased a large chips from the Sandton branch. Before confirming my order and paying I asked the cashier, who happens to be the manager, how long I would have to wait. He informed me that it "will not be too long." After waiting more than 10 minutes I saw a gentleman who came after me get his packet of chips and leave. Around 10 minutes later another lady was given her "medium" chips and I thought " great, here comes mine." Mine came and was not even as big as the medium which the lady next to me was served. It was clear to the lady and I that her chips was bigger than mine, even though mine was a "large." The assistant argued with me based on the packet size and I was not disputing that." Everyone around could tell that my large chips was actually, if not smaller, then the same size. I am disappointed as it is a matter of principle not back and forth with assistants and then the manager. I did not mind the wait, despite being told that it will not be long. But in principle I feel like the sizes are not regulated. Just acknowledge and move on. Do not argue and continue to educate me on packet size when the evidence is clear next to me. Then it was handed to me in a paper bag which 1 minute later fell apart leaving all the chips on the floor. I think staff education is needed.