As suggested by "they" in the comments, the solution was simply to convert the file from dos to unix to replace the line endings.

As suggested in the comments, the solution was to convert the file from DOS text file format to Unix text file format to replace the line endings.

Since the file was in DOS text format, the trailing carriage-return character got added onto the values of both NB_MPI_WORKERS and SEED. In the case of SEED, it didn't seem to be a problem as the value was somehow properly handled by the Python script. But in the case of the other variable, it meant the --n option got a value that was not recognized as legal.