What is the game object measurement unit?

If you look at it from another angle the plane isn't 10x bigger, it's infinitely smaller.

A plane is exactly 10 x 10 units. You can use a Quad ins$$anonymous$$d. It is 1 x 1 units.

i am missing something, i have the scale (10,10,10) for the plane and have to put the cube with (100, 100, 100) to get near the size of the place.

You need to set the scale of the plane to (.1,.1,.1). So the size of a Plane when the scale is (1,1,1) is 10x10. The size of a cube when the scale is (1,1,1) is 1x1. So to get them to match, you need to shrink the plane to 1/10 its original size.

Note you can use the CreatePlane editor script from the Unity Wiki, and build a plane to any size you specify (including 1x1).

i think i understand. The default size of the plane is 10x10 and the default size of the cube is 1x1 and there is no way to change the size at the Inspector, you can only change the scale. is that it?