In episode 10, "Ganymede Elegy", the watch has a dial that has numerals 1 - 15 on it (it figures prominently in the story's plot).
It takes 7.15 Earth days (around 172 Earth hours) for Ganymede to orbit Jupiter and the orbit is synchronous. Even if you artificially give Ganymede a 15 or 30 hour day, the numbers don't add up to a complete planetary rotation.
So, what exactly is the watch suppose to be keeping track of?
