The default UI scale for the JJS tutorial appears to be 100 on the scale slider, based on a tutorial showing the interface scale range and stating the default is set to 100.

For context:

  • The UI scale can usually be adjusted from 50 to 200.
  • A value of 100 means the interface is at its normal/default size in that tutorial.

If you meant a different JJS tutorial or game-specific setting, the exact default could vary by version or platform, but the source I found points to 100.