well I know the trick ..........
what ever the two digit number you choose and add up them and then minus from that number it always results in multiple of 9 and they always place similar symbol on the numbers which are multiple of nine.....
now as the screen change they change the symbol but the logic remains the same and the symbol what ever it is remains on the numbers multiple of nine and then if you choose another number then again you find that what you have choosed it is showing the correct answer and also you think that you have choosen the different symbol with different number,
but if you do it 2 or 3 times you will find all things happening according to above story,...
thanx
..................................... myth busted
