Question AR wireframe with a real car model

Hi guys
If i've a 3D model in real scale 1:1 ad import this in Unity, match with 1 unit / 1 meters.
Why if i use ar Fondation when instance the model with the right scale or with image target or instance it at mid air, this is always more small than real car?
About a 15/20% of smaller size than real.
I've try to instance at 0,0,0 position so it's impossibile to have a perception error but nothing.

Any suggestioni?
I've check more than one time the right prefab scale before and after the instance.

 

If you're using an image target to instantiate the object, you need to make sure the image target size is set correctly to the size it is in the real world.

In the XR Reference Image Library, make sure your target has 'Specify Size' checked, and then set the physical size. This way the object that is instantiated from this target will have the correct size relative to the target.