Just before the final shootout Odom says "Three rounds..." before reinserting his pistol's magazine and racking the slide. Given that the slide wasn't yet locked back that means a round was still in the chamber so in racking the slide Odom effectively ejected one of his desperately needed live rounds.
The paramedic on the ambulance reports Dobson's blood pressure as 70 over 42 - dangerously low - but as he says this the camera pans across the monitor screen which clearly reads a BP of 115 over 92.