Mathematically, your final answer will always be a multiple of nine. If you notice, all the multiples of 9 (9, 18, 27, 36, 45, 54,63,72, 81, 90, 99) all have the same symbol, so no matter what number you originally chose, you will get the same symbol.
If you click to try again, the symbols all change so you don't realize that they're the same, but the ultiples of 9 will always all be the same symbol.
Clear as mud?