It seems that 19th-century tile makers sometimes used clay tiles as memo pads. Cawarden Reclaim (who found that dismissal notice) stumbled upon another tile that contains an order list:
This is an old handmade pan tile, made on 21st July 1802. [...] Reading the information, it seems that this is an order list for the maker. With no paper and pen to hand, the words were jotted down on a freshly formed clay tile, which was waiting to be dried out and fired. This tile was fired, used on a roof, and remained in place for approximately 220 years.
I imagine that it was like writing a dismissal note on the white board after a heated office argument.