This page provides more detailed information about index compression during Oracle Data Pump import.
NONE is specified, then the index compression clause is omitted (and the index is given the default compression for the tablespace). However, if you use compression, then Oracle recommends that you use
COMPRESS ADVANCED LOW. Indexes are created with the specified compression.
If the index compression clause is more than one word, then it must be contained in single or double quotation marks. Also, your operating system can require you to enclose the clause in escape characters, such as the backslash character. For example:
Specifying this parameter changes the type of compression for all indexes in the job.