distance lines

hi 

yes it's again and always me !!!

i understand nothing:

i am drawing in 3d model with line tool and i m writing in the command my distance, longer 3 for example but i haven't 3 like i wrote, i ve got a small distance. so i don't understand, and unity of my draw is good, it's in mm, so ... i don't know.

Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.