Final Fantasy 7 Timer choice explained: What's the difference between 20 or 30 minutes? Upon reaching the reactor, Barret will insist that you place the bomb to prove your loyalty to Avalanche. You can either set the timer to 20 minutes or 30 minutes. Your choice of time makes no difference to the story or the success of the mission. The only real difference you'll experience is a line of dialogue from Barret after you've set the timer. The timer also doesn't come into play, until after you've defeated the Scorpion Sentinel, which means you can take your time defeating the boss without pressure. If you pick 20 minutes, he'll say: