You estimate that there is enough of this chalk left to draw a single summoning circle and accompanying runic pattern.
>draw sum circ
Using some fine crystalline chalk, you outline the shape of a summoning circle upon the ground.
Your crystalline chalk disintegrates!
Roundtime: 3 sec.

Measure LIED TO ME! can I have free chalk now? :D

ha thats a letdown. simplest coding solution for both GMs and PCs is just to have the game automatically discard chalks that only have 1 "draw" left (after a rune pattern is drawn with it). ie your chalk has 3 "draws" left-->you draw a circle and a pattern with it-->automatically toss chalk aside