Boxshadow offset y doubt


Was going through the box shadow for first time. Noticed offset x with positive value will move the shadow to right and negative value will move the shadow to left. But when it comes to offset y, negative value put the shadow at top , should it be rendering the shadow at the bottom as the normal y axis with negative value will always be at the bottom ?

That would be the case for a regular Cartesian plane. But on computer screens, the y-axis is positive downwards.