Digital cameras/meters are biased toward underexposure to avoid blown highlights, just as you would expose with slide film. My wife shoots an XT and brackets everything and she/we consistently choose the -1/3 stop exposure as best exposure.

Take a white piece of printer paper outside on a sunny day and measure with the meter, then open 2 1/3 stops and that should be a pretty good exposure. Or the palm of your hand on a bright sunny day and open 1 stop. This also should be darned close to proper exposure and both will typically agree with the Sunny 16 rule, f16@1/ISO film speed.

My Digisix, designed primarily for the digital market, is about -2/3 stop compared to my Pentax V and other meters of the same vintage.

-Fred