Parking & Customer Service & fining me £100 for 13min !!

I visited Caernarfon store to do my Christmas shop. It's a small store with an even smaller car park which is regularly log jammed with cars trying to park. I did my shop in a busy store and then joined the massive lines at the till. It took quite some time to be served but hay it's christmas. I finally left the shop and loaded my car. Then I had to wait while cars blocked the car park looking for parking spaces. I finally left. Today, 31at Jan 2018 i receive a parking fine for £100 for overstating in free parking for 13mins !! £100 !!!!! omg if youd of staffed your store during this peak season with enough people on the tills and ensured people didn't block the car park then I wouldn't of overstayed by 13mins. And you want £100 reduced to £60 if I pay by the 7\2\19. Me overstating is down to your company not having enough staff on the tills so is this your way of making even more money out of your customers ?