Significant figures are numbers that are higher than 0, and before the decimal.
For example:
12.0, there are only 2 significant figures: 1 and 2. Since 0 is not higher than itself and is after the decimal, it is not a significant figure. Trailing 0’s are not significant. Only zeros that are in between a number are considered significant.
For example: 302 has 3 significant figures.