Basically it means that that option as displayed is not being applied. Either it's being set by a more recently read config file or it's set in the config.sup and can't be overridden.
In case you're not familiar with them, config files are read in this order:
1. Config.sup in the loadpoint (typically C:\Program Files\PTC\Creo 3.0\M020\Common Files\text)
2. Config.pro in the loadpoint
3. Config.pro in the home drive (if set)
4. Config.pro in the startup directory (working directory)
If this option is set in the config.pro in step 2 and then again in step 4, when viewing the file in step 2 it will show it grayed out.
Likewise, if this option is set in step 1 and also in step 4, when viewing the working directory in step 4 it will be grayed out.
Make sense?
Tom U.