When the island is set to self destruct, the last time the timer is shown it says 00:30:00. After a while, when the voice start counting down, it starts at 10 but it should start at 3. There were 27 beeps between the shot of the timer and the countdown voice.
In the final scene, an American recruiter for the game (played by Cate Blanchett) is playing ddakji with a potential contestant in some alley in California. This doesn't make any sense since it's a Korean game and neither the recruiter nor the random American man on the street should be familiar with it.