How can i define the origin party number and final ?

Can i use the trackNumber attribute?

In previos versions i use the xrefci value, the lower one was the calling party number, however in version 11 that's not a constant

{
  "eventBody": {
    "sessionState": "CLOSED_NORMAL",
    "callControllerType": "Cisco-CUCM",
    "sessionId": "47f155a7d705662",
    "urls": [
      {
        "rtspUrl": "rtsp://10.0.0.1/archive/47f155a7d705662"
      },
      {
        "mp4Url": "https://10.0.0.1:8446/recordedMedia/oramedia/mp4/47f155a7d705662.mp4"
      },
      {
        "wavUrl": "https://10.0.0.1:8446/recordedMedia/oramedia/wav/47f155a7d705662.wav"
      },
      {
        "httpUrl": "https://10.0.0.1:8446/recordedMedia/oramedia/mp4/47f155a7d705662.mp4"
      }
    ],
    "sessionStartDate": 1467399734796,
    "tracks": [
      {
        "trackStartDate": 1467399734796,
        "trackDuration": 45985,
        "downloadUrl": "https://10.0.0.1:8446/mma/ExportRaw?recording=47f155a7d705662-TRACK1",
        "codec": "PCMU",
        "trackNumber": 1,
        "trackMediaType": "AUDIO",
        "participants": [
          {
            "participantStartDate": 1467399734796,
            "deviceRef": "988887976",
            "isConference": false,
            "xRefCi": "35388995",
            "participantDuration": 45985,
            "deviceId": "Gateway1_PSTN"
          }
        ]
      },
      {
        "trackStartDate": 1467399734796,
        "trackDuration": 45985,
        "downloadUrl": "https://10.0.0.1:8446/mma/ExportRaw?recording=47f155a7d705662-TRACK0",
        "codec": "PCMU",
        "trackNumber": 0,
        "trackMediaType": "AUDIO",
        "participants": [
          {
            "participantStartDate": 1467399734796,
            "deviceRef": "3206",
            "lineDisplayName": "Marketing",
            "isConference": false,
            "xRefCi": "35388994",
            "participantDuration": 45985,
            "deviceId": "SEP001FA2B8F480"
          }
        ]
      }
    ],
    "sessionDuration": 45985,
    "callControllerIP": "172.16.28.101"
  },
  "eventType": "SESSION_EVENT",
  "eventAction": "ENDED"
}