Threshold is basically the inactivity period of the users. The Threshold setting allows you to set how much after the last activity should a user be considered inactive (in seconds). The shorter the period, the more aggressive you are in saving licenses.

Example: Let's assume we have a single user license and two users: "A" and "B. User “A” logs in and starts to use Confluence. User “B” will only be able to log in if user “A” was inactive for at least the time specified by threshold (ie. did not click on anything within Confluence for that time). The license of user "A" will be revoked only after that amount of time.

Check this option if you want the License Optimizer to start automatically after app update or Confluence restart.