The timer on your Trio panel is configured in countdown mode. This means the lower value (SV) will be where the countdown timer will start at in minutes.
When you press SET:
T1 = Countdown time you want to wait
T2 = How long you want the buzzer to sound
To set a time:
Press "set", then the "up" or "down" arrow until you reach the desired count down time.
Press "set" again to change the buzzer alert time length.
Press "set" 2 more times, which brings you back to the main screen.
Press "start" button to begin your countdown!