where can I set the arg “box_min_x”？

[ClockZinc]

The readme says that the exploration range can be set by this:

but I CANNOT find any place to change!
Finally, I found the code that can modify the search range of the drone in RACER/uav_simulator/map_generator/src/map_publisher.cpp

It's not as stated in the readme that modifying the launch file can solve the problem. Besides, the readme seems to be copied from FUEL's...