MediaSettings Callback Mode being updated?

Platform API
1

Hello,

We're using the JavaScript SDK to update some queues. Upon checking the audit viewer, we noticed this change to the queue:

 {
      "property": "Queue/21b0ec93-d07c-4a56-9fb5-e71633f451cd#mediaSettings/callback:mode",
          "oldValues": [
            "AGENT_FIRST"
          ],
          "newValues": [
            "null"
          ]
        }

Trying to find what "callback.mode" is but no results so far. When doing a GET request to our other queues, no property is found when looking for callback.mode: "AGENT_FIRST"

Please advise what is being changed here?

Thank you!