Classic British Flight Sim

Or in this case, coffee dregs.
I was stunned to see this today.
Obviously, a tall, dark tortoise is coming into my life

Ahh, you have been visited by the spirit of Great A'Tuin and the ring around the outside represents the edge of the Discworld which he carries on his back!

You are a very lucky man!

https://en.wikipedia.org/wiki/Discworld_(world)

Having little experience in tasseography , My guess is: it's a reminder from the missus to wash your cup.