Systems that have not yet run a compliance check have not sent in the necessary events to have a valid compliance status. Previous to 7.1 the report would simply omit those systems that had the policy scheduled but had not yet run the compliance check. As this would create results that did not include all systems targeted a development defect was created (ET#2018809). For 7.1 the Compliance reports were rewritten to show all targeted systems. Those systems that have not yet returned a compliance status will show a status as "Not applied". This allows an administrator to properly track a policy deployment, and can know how many systems have not yet run compliance checks for the policy.
The "Not applied" status is used as we do not yet know if a targeted system is compliant or not.