Pan And Tilt Building HELP

Hi,
I am currently in the process of build my pan/tilt kit, in the pictures there is 12 holes in the circles the bits fit onto and the screws supplied can fit in it (when i say pictures i mean the instructions show) But my circles have 18 holes and the screws don't fit.
Am i doing something wrong?
I am currently in the process of build my pan/tilt kit, in the pictures there is 12 holes in the circles the bits fit onto and the screws supplied can fit in it (when i say pictures i mean the instructions show) But my circles have 18 holes and the screws don't fit.
Am i doing something wrong?