Little Used Index
This warning has been raised because SQL Server's statistics suggest that this index has only be used for a small percentage of queries on the table. If an index is used solely for a small proportion of queries, then it may be beneficial to drop the index, to reduce the overhead of maintaining it, and letting that small number of queries run without it (or fall back on another index).
NOTE: This warning is purely based on SQL Server's statistics, which are only populated by querying of the database. If the database has just been restarted or restored, or it's a replica database that is never used for selects, then the statistics will not accurately represent whether the index is used or not.
Consider removing the index.
Any suggestion from Aireforge should be thoroughly tested before being implemented into production.