It's simple. This app starts counting from 0 up when you click play and stops when you click pause.
There are settings allow you to change the time interval or the number font size. And we are having a list of functions to be added in the next version.
About what is this app used for, practicing concentration exercises, measuring one activity time, meditation, or helping you fall asleep are what we can imagine now. Let us know what else you can do. All feedback are welcome.
Thank you very much.