What is the origin of YOLO/darknet coordinates

I am aware of that darknet/yolov3 outputs relative coordinates, would the coordinate (0,0) be at the bottom left, or at the top left?

I am confused as opencv2 seems to have the y=0 at the top of the image as is usual when working with matrices. Yet mathematicaly and intuitively (for me at least) the coordinate (0,0) should be at the bottom left.

(0, 0) is top left.