Coordinate naming

Watching the tutorials on the camera part I'm puzzled why the X and Y appear to be swapped from the conventional approach where X positive is to the right and X negative to the left while Y positive is upwards on the page and Y negative is downwards.

Search XY coordinates on the web (or look in a math book) and you see this sort of thing.

www.techtarget.com

What are x and y coordinates?

X and y coordinates are the horizontal and vertical addresses of a point in any 2D space and help identify the exact location of a point. Learn more here.

So why on the video part is the X upwards?