‘Abdullah ibn ‘Amr رضي الله عنهما said: "I saw the Messenger of Allah ﷺ counting the words of glorification on [the fingers of] his right hand." [Abu Dawud 1502; at-Tirmidhi 3486; Sahih Sunan Abu Dawud 1/280].

The Messenger of Allah ﷺ said [to the women]: "You should say 'Allahu akbar,' 'Subhanallah,' and 'La ilaha illallah,' counting on your fingers, for they will be asked and made to speak." [Abu Dawud 1501; at-Tirmidhi 3583; Sahih al-Jami‘ 4087].

Thus the Sunnah is to count the words of glorification on the fingers of the right hand — this was handed down to us from the Prophet ﷺ himself and was the practice of his Companions رضي الله عنهم.