The countup timer is displayed prominently in the upper center area of both the main page and the switchscreen. It lets you know how long you will have to wait before the music stops again. Whereas the left side of the equation shows how long the music will play (so that number does not change while the music is playing), the right side counts up to meet that value during playback. Note: the training is about using the switch when the music ends, rather than watching for the timer to stop.
We do not use a countdown timer because that emphasizes counting backwards.