There is a mistake. This would have been correct if there was something that said each servant can taste the wine only once, or there is a time constraint of some sort. For this problem, make the servant #1 drink from bottle #1. If he dies, then thats it, over. But if he lives, make him drink from bottle #2, etc, and find out the bottle that is poisoned, and you have at-least 9 servants left!