Unix   On Unix, the level is an integer from -20 to 19. The default value on Unix is the same as the nice value of the parent process. Lower level values represent a more favorable scheduling priority. All restrictions placed on setting a nice value apply to the -gb option. For example, on most Unix platforms, only the root user can lower the priority level of a process (for example, changing it from 0 to -1).

Windows   On Windows, normal and high are the commonly-used settings. The value idle is provided for completeness. The value maximum may interfere with the running of your computer.