Golden ratio spiral and digits on forearm

I have finally got into the seed vault, and I am writing this on the back of a ration chit because the good paper has gone to the hydroponics board. Your grandfather would have crowed. For forty years he told anyone who would listen that the ratio sits under everything that grows, and the orchard drones only started planting in spirals after the council read his old notebooks.

Down on the third shelf there is a steel plate no bigger than my palm. Someone has scored a golden rectangle into it, divided into squares, with a quarter circle curling through them like a shell. Above the squares run rows of digits, 1.61803398 and then a scatter of others, but the plate stops after the eighth place as if whoever made it ran out of room or nerve. I sat on the cold floor for an hour working the next figures through in my head, and they came out clean, as if the number had been waiting for someone patient enough to ask.

The last page of his notebook has the same looping hand. It says only: keep the spiral open at the end. I have spent three nights among the seedlings and realised the curve never closes, each turn sitting a little further out than the last, which is why nothing in the orchard crowds its neighbour. The plate is the map, Imke, and the map is still blank past the eighth place.

So I have taken a stylus to the steel, very small, and added the ninth digit myself. It is a 7, which I suspect is wrong, but it is mine to be wrong about. Put the kettle on when you read this, and do not let the drones tell you the sums are finished.