To know exactly the meaning of the bounding box coordinates, check this https://support.catchoom.com/customer/portal/articles/1886553
Note that the coordinates are relative to the query images. The query image is rotated 90 degrees on iOS when the phone is vertical (because of the orientation of the sensor). You should normalize the coordinates using the view size and aspect ratio of the camera frame (HD by default, 16:9). The frame is fit on the screen so that it maintains the aspect (no deformation) and it is cropped on the sides (when the phone is in portrait orientation.