The first column shows the shape of "pebbles" used for the various units of a Sumerian number.
The equivalent impression in clay tablets is shown in the centre column. Two round sticks of different diameter were used for the impressions. The symbols for 1 and 60 were produced by oblique impressions, those for 10 and 3600 by vertical impressions. Other numbers required a combination of impressions from both sticks.
Cuneiform writing started shortly after 3000 BC when the two sticks were replaced by a thin stylus. The Sumerians then simulated the stick impressions through stylus impressions. The right column shows the result: the Sumerian numbers in cuneiform.