For OG, it could be a finer crush or technique that's getting you better efficiency. How are your volumes. If your pre-boil OG is right on, but you collect extra wort to account for boiloff, the extra water might extract extra sugar. If it's consistently high, then pat yourself on the back and adjust the attenuation percentage in Beersmith.
For FG, that seems harder to diagnose. It could be mash temp, mash time, particulars about your recipe. Simple sugars are fully fermentable but Beersmith doesn't seem to account for that. My first cheap digital thermometer was 10 degrees off.