If you open a Word document and save it but don’t do anything to it, how much editing time does that count as? If you leave it open, go on vacation, come back two weeks later and type something in it, how much time does that count for? Does it count the time in which keystrokes are happening? How does it determine the beginning and ending points of when the keystrokes are happening?
Isn’t it just clock time? That’s what I always thought. Whether you’re typing away or not should not be factor. Just open a file, let the clock run, and check how the total editing time has changed. Easy.
Not sure how it works, although i suspect that nivlac is probably correct.
But surely it’s pretty easy to do your own experiment? Open a new document, name it, and save it. Then walk away and come back ten hours later. Check the editing time, and you should have your answer.
Well, you guys are right. It measures the length of time you leave the docucument open, even if you never touch it and leave the window inactive the whole time while you go and spend hours Doping in your browser instead of editing in Word.
WTF good is that? 
It can’t possibly give an accurate reading of how hard you slaved over the document. Not even remotely in the ballpark. Everybody at some point will walk away from their desk leaving a document open.