Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
(1) d can be any multiple of 25 (25, 50, 75, and so on)
(2) d can be any multiple of 40 (40, 80, 120)
(combined) d has to be a multiple of 200. But even then we don't know if it's 400, 1600 or any other multiple of 200 that is a perfect square.