How many points is line spacing 'single'?

[Ugeen]

I have a question regarding line spacing. By 'line spacing' I mean the thing described as line spacing in this picture:
http://www.flickr.com/photos/nicksherman/5640736164/ . I am assuming that line spacing in Word measures the thing that is called 'line spacing' in that picture.
(If line spacing does not mean that, then what does it mean?)



Let's take an example: font=Times New Roman, font size=12 (i.e. 12 points). Now, how many points high is line spacing when line spacing in Word has the value SINGLE?
I suppose it is 12 + leading. But what is the default height of leading in Word, and has this changed in different versions of Word.