Significant figures refers to digits within a number which must be included in other depict correct quantity of the figure.
4.29478416 = 4.2947842 ( 8 significant figures)
4.29478416 = 4.29478 (6 significant figures)
4.29478416 = 4.295 ( 4 significant figures)
4.29478416 = 4.3 (2 significant figures)
To round a number to a certain number of significant figures,
Only leading 0 which comes before the decimal Point are regarded as insignificant.
Once the number of significant figures have been identified, the next number after this is either rounded up to 1 and added to the last value(if number is ≥5) or rounded to 0 (if number is less than 5)