An RRS panel user has attempted to specify a sort order that is not contiguous starting from the number one (1). RRS expects that the primary sort key will be specified as sort order 1, the secondary sort key specified as sort order 2, the tertiary sort order specified as sort order 3, and so on. If a secondary sort key is specified, a primary key must be specified. If a tertiary key is specified, then a secondary key must be specified, and so on.