The police record of the butler played by Brandon Hurst shows his age as 36. However, the photo is of Brandon Hurst in 1935 when he was 69 years of age, having been born in 1866.
O'Leary finds a semi-automatic pistol in Mittie's dresser, then tells Sarah a cartridge is missing from it. It would not be possible for him to know how many cartridges were loaded in the gun to begin with.