strokes-grid-resolution

strokes-grid-resolution is a variable defined in `strokes.el'.
Its value is

9

Documentation:
Integer defining dimensions of the stroke grid.
The grid is a square grid, where `strokes-grid-resolution' defaults to
`9', making a 9x9 grid whose coordinates go from (0 . 0) on the top
left to ((strokes-grid-resolution - 1) . (strokes-grid-resolution - 1))
on the bottom right. The greater the resolution, the more intricate
your strokes can be.
NOTE: This variable should be odd and MUST NOT be less than 3 and need
not be greater than 33, which is the resolution of the pixmaps.
WARNING: Changing the value of this variable will gravely affect the
strokes you have already programmed in. You should try to
figure out what it should be based on your needs and on how
quick the particular platform(s) you're operating on, and
only then start programming in your custom strokes.

You can customize this variable.