Continuity mistake: After Sharpe and Stamper have the argument on the asteroid, Truman says they need the radio back up. When he says this, you see the countdown clock for the asteroid which is at five hours and 12 minutes. A bit later in the film, after the nuke was shut down by a technician at NASA, one of the Air Force Sergeants takes the terminal. In the background, you can see the clock again but the time on it is at six hours and 49 minutes.
Picture added by Ronnie Bischof