Owl-vit bounding box format

I’m using Owl-Vit and I have a doubt regarding bounding boxes format.

Which is the format used by Owl-Vit? starting from the Colab:

I suppose is [X,Y,WIDTH,HEIGHT]

Why is not [X,Y,XMAX,YMAX]? How can I change the bounding box format?

And, why sometimes OWl-Vit returns negative coordinates? What does it means? Can I simply put to zero or is something wrong?