It will be 3 hours before your flight, plus or minus 15 minutes.
Keep in mind that the time you are assigned is the time your bus leaves. You need to be at the platform - completely ready to go - 15 minutes before that. You'll also need to allow plenty of time to get your bags from bell services and make a final trip to the bathroom. You should plan on being back at the resort an hour before your scheduled pick up time.