Is somebody know this function of geometry editing ?

Hello, everyone. I’m new here and I’m making project of a road map for autonomous driving system testing.
Now I am facing a problem, I want to create road piece with a structure of trapezoid. here is what I make it : I set a cube in and make the z=0 to become a flat,and with the geometry editing I drag a point in one corner and it becomes a trapezoid, but I want to know how many length unit I’ve dragged, Is there anywhere that I can manually input a the expected number of dragged length unit for the flat or the information of the four points from four corners ?