EigenFaceRecognizer usage

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I'm trying to use Eigen recognizer in C++ code and it looks oddly for me, please correct my dev logic if it's wrong : example scenario:

• there is a database of the photos with user ids (more than one photo per user id)
• I'm training the recognizer with e.g. user id = 29 (5 photos), and user id = 2 (4 photos), so input vectors are (first column is a labels vector, second one is grayscaled Mats):

29 - 1th user's photo1

29 - 1th user's photo2

29 - 1th user's photo3

29 - 1th user's photo4

29 - 1th user's photo5

2 - 2th user's photo1

2 - 2th user's photo2

2 - 2th user's photo3

2 - 2th user's photo4

• for the testing only , I'm using first photo of user id = 2 as input

• the results looks oddly : confidence = ~40.000, but label = 29 (supposed 2 as user_id during the training in labels vector)

what is wrong in such logic?

thank you