here is the reason:
tiled-display will be default value 0 because it is not be set, the pipeline will include nvstreamdemux and four fakesinks, there will be four probe functions latency_measurement_buf_prob on the four sinks( you can debug in create_pipeline()). after inferencing every frame, usermeta will be copied in four copies by nvstreamdemux , and latency_measurement_buf_prob will be entered four times, so there will be the multiple same printings because the usermeta is the same, batch_num is a global ,variant, it will changed every time.