As I said this is an old feature from rF1. I don't think either ISI or S397 uses the prefix for kerbs any more. @Tuttle ? From many years since now 3d surfaces using one of the available road material are used to model kerbs. If different material to the main track one is used is basically to assign different grip values since they are typically painted and should be avoided in rain for example. So as a summary and as I already said, in most tracks the parameter will have no effect.