I opened one of them in a text editor and it looks like they are logged error and warning messages.
Examples:
[01:16:06.225884][WARN][mediabox][gstlog][gst_dxgiduplicatorsrc_prepare_output_buffer:437] Invalid crop region w:-2147483648, h:-2147483648
[01:16:06.241832][ERROR][mediabox][mbplugin][gst_dxgiduplicatorsrc_calculate_crop_region():397] GetClientRect(src->window, &rc_window_client_rect) is failed and return.