What is the distance scale from real world to game?

I used Kephallonia to measure the game distance.

From one tip to the other is 1298 meters.

I used Apple Maps to route a similar distance on Cephalonia (as it is now spelled, I guess).

Apple Maps lists the distance as 41 miles.

41 miles is 65.983 kilometers. That is 65983 meters.

1298 / 65983 = 0.01967

65983 / 1298 = 50.8

So the scale of game world to real word is 1:50. If your character walks 100 meters then you yourself would have to walk 5 km.

To put it another way, the developers shrunk the real world to 2% of its original size.