To understand why there is an unspecified line item while checking the Analytics report with Occurrences metric, we need to understand the following definitions and scenarios.
Occurrences higher than Instances: This outcome is expected for conversion variables, as occurrences also includes the number of times the variable was defined (instances).
Instances higher than Occurrences: This outcome is not possible in reporting, as all instances are recorded as occurrences as well.
Occurrences vs. Instances : Occurrences count hits where a dimension item was set or persisted. Instances do not include hits where a dimension item persists.
Occurrences vs. Page views : Occurrences include all hit types, including page view tracking calls ( t() ) and link tracking calls ( tl() ).
The page views metric only includes page view tracking calls, and excludes link tracking calls.
While running page report(OOB) report with metric Occurrences , it is expected to get Unspecified line item because of s.tl() call which happened during the visitor journey even if the s.pageName variable is set explicitly. To overcome this it is recommended to create a custom analytics variable (prop/eVar) to capture page name into it.
Note: Subrelation is synonymous with conversion report breakdown.