What does Interstitial timeout mean in admob?

Question

When I create an Interstitial ad unit in the Admob page, it asks to input an Interstitial timeout:

Determine how long to display the interstitial ad. Valid range is 3 to 10 seconds and must be a whole number.

But as far as I know Interstitial ads only close when we touch the close button or when we press the back button on Android phone right? So what is it?

Answer 1

Why that option is there is a mystery. It seems to serve no purpose whatsoever.

There are several posts on Google Groups, Google AdMob Ads Developer, reffering to this issue and all point to it not working. You can not close a interstitial after a X second timeout.

Excerpt 1 (Google employee, forumpost):

As a publisher, there is no way to do this. The SDK doesn't have any hooks to autoclose the interstitial...

Excerpt 2 (Google employee, forumpost):

It is intended behavior that an interstitial requires explicit closing by the user.

Excerpt 3 (AdMob employee (slightly oblivious), forumpost):

You actually can't hide the interstitial after a few seconds, because it's its own activity.