How many Christ-rejecting people will be living at the time of God's wrath in the Tribulation?
No specific number is given. The context says that during the last three and a half years of the Tribulation, when God pours out His wrath, the vast majority of Christ-rejecting people will be living at that time. So the answer is a vast majority, not a numerical count.
Les explains that world population has doubled repeatedly, reaching about 4 billion and then 8 billion by 2020, which alarms prophets of doom and intellectuals who want drastic population reduction. But he says God has His own timetable, and he will not worry about a population explosion. In that setting, Les teaches that when God's wrath is poured out during the last 3-1/2 years of the Tribulation, God has every right to act because the vast majority of Christ-rejecting people will be living at that time.