This means that every host that hasn't reported in the last 5 minutes is out of sync. With Puppet the default interval is 30 minutes which means that most of your infra is out of sync all the time. commit:348ec9c0d6ff6c2574c5e6dddbe8e9203d73d2e8 introduced this setting.
Created from redmine issue http://projects.theforeman.org/issues/24350
Upstream bug assigned to sgraessl
Moving this bug to POST for triage into Satellite 6 since the upstream issue https://projects.theforeman.org/issues/24350 has been resolved.