Hi,

Thank you very much. This is indeed a great and detailed answer.

The width value can arbitrary. It is used to establish the unit scale of your Unity scene - all of the objects in the scene will be measured in relation to the width of your target. So if you define the width based on your printed target's width in CM then the scene will be in CM, for example. You could also use the image's pixel width, or any other value you choose.  But you should always define a width that is greater than the distance of the near clip plane of the camera, or you may find that the augmentation becomes invisible at near distances.

*It can be useful to use a measurement of the physical target because this will enable you to estimate real distances and dimensions, such as how far the user is from the target they are viewing.