Cool down times

Have you ever thought that the last seconds of a cool down timer are slower and slower?I used a stop watch and timed one cool down of a skill (shown as 16s), and started my stop watch when I saw 15s left. As the skill was again usable I stopped and read 16.5s on my watch.I will validate this a few more times, but it seems when the cool down shows a digital fraction, it goes slower.