To visualise SLA overdue statistics add a gadget to JIRA dashboard:

Add value in the field:

• Title - a title of this gadget;
• Project or Saved (Filter) - Project or saved filter to use as the basis for the graph;
• SLA field - choose SLA field;
• Metric -  choose a metric
• Group period - choose a period;
• Period type - choose a current period.

You can configure it to show only overdue SLA or SLA on time, or both of them as well.