The logic is quite simple. Any number u choose and apply the calculation, you will end up with a multiple of 9. Look at the symbol chart, all the multiples of 9 have the same symbol. Every time u play, the symbols change, but the 9-multiple symbols are all same. So even if u dont think anything and click your mouse with your eyes closed, the symbol which will appear will be a 9-multiple symbol. Very ingenious.... :D