Why does data.zip contains 9 fields in its groundtruth data (for mot_challenge)? (when it is actually recommended to have 10 fields)

[yushakareem]

I downloaded data.zip file as recommended on the repository Readme (https://github.com/JonathonLuiten/TrackEval#quickly-evaluate-on-supported-benchmarks). I noticed that gt (groundtruth) data for the mot_challenge contains 9 fields.

Whereas, on the TrackEval repo (in the docs) it is recommended that there should be 10 fields (https://github.com/JonathonLuiten/TrackEval/blob/master/docs/MOTChallenge-format.txt).

Please can someone help me understand how/why there are 9 fields in the gt (groundtruth) dataset in the data.zip file provided by TrackEval.

Thank you!