What is normal power down cycle?

[Magnetic1]

I have noticed since ios 7 update that my ipad mini powers down in different durations.
One takes 2 seconds and the other takes 15 seconds.

But I did a test to see if I can reproduce the 15 seconds power down.

And it seems that I have to power down first when it takes 2 seconds and then power up and then power down again to get the 15 seconds power down.

This seems like a real waste of time investigation, but my concern is that I maybe seeing a video of a power down and power up via mirroring.

I suspect this because sometimes the battery level indicator changes really fast and when I jump from one app to another the screen goes to an old screen just before updating.

Any idea what is going on?
Thanks.

 

[Magnetic1]

One more thing, several times after the 2 second power down, a double click on the home button invoked my ipad mini to show the power up sequence, or video.
But I can't turn on the ipad mini using the double click of the home button at other times.

 

[dhewson777]

I'm not sure I'm understanding your post.

Firstly, what do you mean by power down? Are you taking about holding the power button, then swiping to turn off the iPad?

If so, I don't get why any "shut down" time variation would be a concern.

The rest I just don't understand at all, especially the mention of mirroring.