Hasta La Motion!

I’m trying to get around with matchmoving and Ive just started off with Autodesk Matchmover.
Referring to the bundled tutorials, it has a chapter on supervised tracking. The tutorial just mentioned that the distance between 2 corners of the room was "20". 20 of what? It left me with some more questions:

I can upload a frame from the sequence if it could help.

1) Did they know the set measurements? (probably yes !!)
2) What units setup matchmover uses? i.e. cm, meters, inches etc.

And some more general questions:
1) Is camera data(like focal length, apertures, distortion grids) given to matchmovers?
2)Do matchmovers always get access to set data? And in its absence, what do they do?

These questions actually made me download a book on the same topic authored by Tim Dobbert.
Just wondering if someone could help out!!