How does the LightGBM regression example work?

Question

Machine learning

There is such an example:
https://github.com/Microsoft/LightGBM/tree/master/...
Help me figure out what exactly is obtained in LightGBM_predict_result.txt
I understand correctly that with the command:
./lightgbm config=predict.conf
predict the first column? And the one that already exists in the input regression.test?
And if I try to slip another example, in which there will be just no data for this first column, but all the rest will be, then in order for this example to work on my data, I will need to add the first column in a special way with unclear what values?