Change the number to scientific notation. It is easier to see. The last digit retained is set by the first doubtful digit. The answer contains no more significant figures than the least accurately known number. 6.82 x 10 - 3 Leading zeros are not significant.
Imbedded zeros are always significant.
Even though your calculator gives you the answer 8.0372, you must round off to 8.04. Your answer must only contain 1 doubtful number. Note that the doubtful digits are underlined. Subtraction Subtraction is interesting when concerned with significant figures. Even though both numbers involved in the subtraction have 5 significant figures, the answer only has 3 significant figures when rounded correctly.