A list of the GRBL machine configuration options are can be found on GitHub.
Use Candle or GRBLControl to read or write GRBL settings. (Any serial terminal program can do the same thing)
Type commands at the bottom of the console area.
$$ returns the GRBL configuration values as shown here
Example: Change the maximum X axis distance to 200mm. The original value shown is 280mm (See $130=280).
Change to 200mm by entering
$130=200
The controller board should remember these values once set.