Set timer duration in Activity

How do I set a timer duration in activity?

   variables.put("duration", 0.5); 

Is it in seconds/milliseconds?

 <boundaryEvent id="boundarytimer1" name="Timer" attachedToRef="approvaltask" cancelActivity="true">
  <timerEventDefinition>
    <timeDuration>${duration}</timeDuration>
  </timerEventDefinition>
</boundaryEvent>