Is leaving 5p after a meal meant as an insult or just odd behaviour?

I used to waitress at weddings and I once waited on a table where either the bride or grooms grandparents were sat. So this was almost 15 years ago and on the table was these grandparents who were easily in their 80s and some other older guests in their 70s at my best guess. They were truly lovely people and we laughed and joked when I served them and they asked me lots of questions and were honestly a joy, and i mentioned a holiday in devon i had coming up. At the end of the night as they were leaving the old lady came up to me and pressed something papery into my hand and said thank you so much for the lovely service and she hugged me and they left. I shoved the paper into my apron assuming it was a fiver or something - later in the evening I was in the kitchen and I pulled it out to look, it was a folded piece of paper, I opened it and there was a 50p in there and the paper was a note that said "treat yourself to an ice cream or two" Anyway, some of my older colleagues laughed and said the old lady obviously hadnt been happy with the service and it was a comically low amount to show that but honestly? At the time and to this day I know that isnt true, she was truly happy with the service and wanted to thank me in some way and yeah, 50p wasnt gunna get me much but the gesture meant the world. Im not suggesting the person didnt know 5p wasnt alot but the point is you can either see the good in people or the bad, up to you!