The output type of net.forward after blobFromImages

I just confuse about the case 2 network output define ( std::vectorcv::Mat outs.)

If the outs is defined (Batch, Classes, Boxes), what is the i of outs[i]
I already know the std::vectorcv::Mat inpMat define is (480, 640, 3) for inpMat[j] and the j is the batch

I reference these code and I want to design the input (many img) and output (batch output),

opencv/modules/dnn/test/test_onnx_importer.cpp at 450e741f8d53ff12b4e194c7762adaefb952555a · opencv/opencv · GitHub

Reproduce

Just follow the code that I paste and I use blobFromImages

    std::vector<cv::Mat> inpMats;
    inpMats.push_back(cv::imread("source/data/zidane.jpg"));
    cv::Mat blob1 = cv::dnn::blobFromImages(inpMats, 1.0 / 255.0, cv::Size(640, 480), cv::Scalar(), true, false);
    net.setInput(blob1);

    //case1
    cv::Mat single_out = net.forward();
   // single_out    Dimensions: 1 x 84 x 6300 



     // case2
    std::vector<cv::Mat> outs;.
    net.forward(outs);
    //net.forward(outs, net.getUnconnectedOutLayersNames());
   // outs  Dimensions: 1 x 84 x 6300  for outs[0]