Significant Figures in Scientific Notation
Only one digit in the prefactor is uncertain. The last figure you record is uncertain. All of the rest are well known.
If the distance is uncertain by only a few tenths of a mile, it is recorded as 9.706 x 102 miles. The last digit (6) is the one that is uncertain.
If the distance is known to within a mile or two, it is recorded as 9.71 x 102 miles. The uncertain digit here (1) is uncertain.