iOS Face Recognition with Turicreate

Question

I implemented face recognition with Vision Framework.
The model is trained with turicreate.

https://github.com/apple/turicreate

But the accuracy is not good.
I am using 200 face images of same person to train the model with turicreate to identify him on the camera view.
But for all faces, the confidence is over 90%.

Do you have any tips for me?
Thanks