Tools needed:
1) A thumb nail (right or left)
2) A 2.5mm Allen wrench:

To reset the calibration to a coarser setting do the following:
Locate the rubber grommet (1/4 in wide X 1 inch long) on the roof of the grounds bin cavity, just to the rear of the discharge chute.

Remove the grommet using your thumb nail to grab it.

Just inside the opening locate the black Allen head screw (2.5mm size).

Using a 2.5 mm Allen wrench loosen the screw by turning the Allen wrench to the left as you face the grinder.

With the Allen wrench still in the head of the screw, slide the screw toward the front of the grinder (about 1/8 in to 1/4 in), and tighten the Allen screw.

Replace the grommet.
Pulling the screw forward moves the grind range towards coarse and pushing it in moves the grind range toward fine. Test with coffee to see if espresso is very fine with both levers all the way up. then test for press pot with both levers all the way down. The calibration only sets the zero point. The design is such that if your press pot is too coarse, your espresso will be too coarse, and if the your press pot is too fine your espresso will be too fine also.
Kyle said also:
I hope this will assist you in setting your Vario up just the way you like it. We do calibrate every grinder before it leaves our factory, but we goofed in choosing a set point that was too fine.
UPDATE from Getting started with the Baratza Vario:
Baratza wrote:Calibrating the Vario with the new calibration screw.
Baratza's first shipment of Vario's (March 2009, serial # 001 to 270) were calibrated at the factory to grind too fine. We then changed the factory setting for the Vario so it could be adjusted fine enough for espresso and coarse enough for Press Pot. Since we made this adjustment at the factory we have had much fewer calibration issues. Beginning with serial #271, Baratza added a secondary calibration screw (2mm Allen head set screw) in a round hole between the discharge chute and the calibration grommet. This calibration screw allows the user to easily adjust the calibration in the finer direction with the grinder running. To make the adjustment, empty all beans from the grinder, lower the Macro and Micro levers all the way to the bottom and run it briefly to expel any partially ground coffee. Press the Manual button and then the Start button. While the grinder is running, raise the Macro arm all the way to the top (Espresso). You should not hear any change in motor speed. Now raise the Micro arm up the midpoint. You should begin to hear the motor slow (or labor a little). If not, use a 2mm Allen wrench to slowly turn the 2mm set screw clockwise (when looking up at the screw) until you begin to hear the motor slow or labor. You are done!
See Baratza Vario Recalibration (PDF) for step-by-step instructions. The videos below demonstrate via sound a properly calibrated Vario: