Hi @rszostak - Thanks for reaching out about this. You may want to check out previous forum threads like this one which are relevant to your question. In short, training data is provided to develop your solution, and test data is provided to assess its performance on a new set of data. The sites provided in the ground measures features CSV are distinct from the sites used for evaluation in the submission format. So you may use ground_measures_test_features.csv as input in generating predictions for the submission format.
For more information you can check the description of pre-approved data sources here.
Hope that helps!