Presumably the value from the calibration lab is more accurate. If not, why bother having it calibrated???
Also, if that last decimal place is truly important, then it is important to understand "conventional mass" which includes a correction due to the buoyant force of the air. Since the density of air (which has a surprisingly large value about 1.2 kg/m^3) can change due to pressure, temperature, or humidity, you may even need to consider those factors. As an extreme case, image trying to find the mass of a helium balloon. If you connect it to your scale, you will get a negative value, even though the balloon does indeed have a positive mass.
A google search of "conventional mass" turns up several web pages with good info on the topic.
Tim F