Question about powering down

I've already got a Power Down running. When I click on my SP, I get the options to Power Down, Deposit or Cancel Power Down. Obviously hitting Cancel Power Down stops the running Power Down, but what happens if I hit Power Down again? Will it run two instances of a Power Down together or does it change the Power Down schedule to match the new click?

Edit: The second question or second part to this depending on the answer to the first, if it runs a second power down instance, what does it power down? Does it power down the full balance from the time it's pressed or does it only do whatever has been earned/accrued since the first power down was pressed?