Hello,
Thank you for contacting Teltonika Crowd Support.
Since the values that you wish to add to the JSON format on the Data to server configuration are static (serial number, IMEI or MAC), you could manually enter them as shown below (where XYZ could be your serial number, IMEI or MAC, %d: date and %a: register data):
{XYZ, %d, %a}
Warm regards,
Wesley