.0005
The greatest error can be quite a bit more than you might suspect. The precision of the number would suggest that it is ±.0005 g. However, digital measuring instruments often have precision that is better than their accuracy.
Here is one with a "repeatability" specified in terms of the standard deviation of the measurements. That is 2 mg. The "linearity" is also specified at 2 mg. Thus, 95% of readings will be within 6 mg of the actual value, even though the mass is displayed with 1 mg precision.
Here is one with a "repeatability" specified in terms of the standard deviation of the measurements. That is 2 mg. The "linearity" is also specified at 2 mg. Thus, 95% of readings will be within 6 mg of the actual value, even though the mass is displayed with 1 mg precision.