During startup, it is set for a certain time (5 minutes, 4 hours) and then shows the remaining time. Reacts to events (link). And depending on the settings, it starts the timer or stops. The initial time is determined by the jql condition.
(One of the possible display options)
The plugin can calculate the time according to the configured calendars. In fields and jql there are corresponding settings.
Tips and tricks
Search functions make it easy to find and sort tasks. More info by link.
(Time in status field) - Find tasks that spent too much time in status. Use to track work by status. You don’t even need to create fields for this!
(Timer field) - Sort tasks by the remaining time and complete them first. It helps to fine-tune the SLA and monitor its compliance.