"Duration" from meta.xml after export. Where does it come from?

[Sorry for the cross-post as I put this also in the Presenter forum. It applies to both that at Storyline so I felt it OK to post here as well...]

When I export a presentation out of Storyline (or Presenter 13) one of the files generated is meta.xml. In that file I can find some attributes of the <project> tag. Here are examples from different exports:

 duration="About 2 minutes" totalaudio="0" totalvideo="118910"

duration="About 10 minutes" totalaudio="480569" totalvideo="0"

duration="About 8 minutes" totalaudio="173143" totalvideo="290640"

Can anyone tell me where that "About X minutes" comes from? I'm assuming it's calculated somehow based on all the parts and pieces of the presentation, but it seems like it could get quite complicated, especially if there are embedded quizzes, user interactions, etc.

The totalaudio and totalvideo numbers don't seem to correspond all that well so the "duration" is the one I'd like to rely upon, if I can.

If the presentation is longer than an hour, would it say "About 70 minutes" or something like "About 1 hour 10 minutes" ? If it was less than a minute, would it say "About 30 seconds" or "About .5 minutes" ?

Thanks for any information you can provide. This is a wonderfully useful piece of information but I need to know what forms it can take before I start thinking about extracting it for display purposes.

-KevinB