The median panel inside edit mode in Blender 3D can feel a bit confusing at first. What it’s actually doing is showing the median value of all the vertices you have selected. If you have selected only one vertex then it will show the exact coordinates for that vertex. Add a second one in the selection, and it will calculate the median value of those two points and display that one.
If you select an edge with point A at x1, y2 and point B at x3, y4 then the x-axis median value will be 2 and the y-axis median value will be 3.