It is asserted that the current text related to input picture and corresponding output picture (i.e., related to syntax element nnpfc_input_pic_output_flag[ i ]) is not clear, particularly when the value of that syntax element is equal to 0. Furthermore, it is also asserted that the current design of NNPFC SEI message related to signalling of output picture should be either modified to make it more flexible such that it is possible for an NNPF to have more than one output picture when it takes more than one input picture, regardless its purpose or be described clearer regarding which input picture corresponds to the output picture when the purpose of the NNPF does not include picture rate upsampling.