Other mistake: When Daniel is playing Guitar Hero with his friends, after he and his friends leave the game to go outside, if you look closely at the TV, you can see that the game is still playing (notes are still being strummed) even though there is no one at the controls. (00:23:05)
Other mistake: When Esther comes into the living room to attempt to seduce John, he is drunk and the first few shots of her are blurred as though it was from his point of view. The problem is that the camera is a couple of feet from the couch. From where John is sitting, the point of view shown in the blurry shots is impossible. (01:35:45)
Answer: The scene when Esther takes 4 bullets out of the gun and asks Max if she wants to play shows that the gun has a 5 bullet capacity. Esther fired 1 bullet at Kate's shoulder, 1 at a glass when Kate was on top of the glass roof and 3 other bullets at Max. At the end of the movie Max fires an extra bullet.