Oh boo hoo, sob sob!

Just call me plain stupid but am confused with my lovely recent purchase of a SportCount Chrono 100, I even watched the demo video clip.

So, you push off pressing the button, get to the end of the lap and press again, then do you press it again once you push off, so kind of give it two presses in quick succession?

It seems whatever I am doing, is wrong.

Advice needed, please.