the right and the thing on the Left refers to the bird on the left so would be natural that the bounding boxes aren't the same but you say if these were corresponding to each other what what would the loss be how well would they do and now if you compute this bipartite matching what you want I guess it's a it's a minimum matching in this case what you want is you four to find an assignment of things on the left two things on the right a one to one assignment this is an example of a one to one assignment everything on the left