I recently configured a "1st response time SLA" for a pilot SD project. SLA is met, if the ticket is assigned to someone or changes status to something else than "open" within 24h. The problem is that "1st response SLA%" reports show 0% on the days when there is no tickets opened? Of course 0% can be a real life situation, but I really checked those days. Is this correct behaviour or have I done something wrong? What is logic behind the SLA calculation?