Answer
Since the uncertainties are additive, the uncertainty may end up exceeding the result if numbers are too similar.
Work Step by Step
In calculating the difference between two numbers, the result becomes smaller; however, the uncertainty is the sum of the two numbers. If for example, we have two values of 1.096 ± 0.001 grams and 1.095 ± 0.001 grams the difference becomes 0.001 ± 0.002 grams or 1 ± 2 mg which can drastically affect further calculations that use this value since theoretically our uncertainty indicates that the difference could be negative.
