Simple on purpose
Tap + to count, − to take one back, and the reset button to start again. On a phone, each tap gives a light tap of haptic feedback, so you can count without looking. The counter goes up to 999 and remembers where you were.
Counting in sets of 33
Many people say SubhanAllah, Alhamdulillah and Allahu Akbar in sets of 33 after prayer. The counter doesn't stop you at 33 or set a target — reset it when you move to the next phrase, or keep counting.