When do zeros count as significant digits and when don't they count?
According to the rules of significant figures, all the non zero digits are significant. Thus (a) when Zeros are present between the nonzero digits are always significant.
There are four significant figures in the measured value 8.098
On the other hand,
(b) when zeros are present in the end of a number and the number contains a decimal point. Then it is considered as a significant figures.
For example: 0.8900
Therefore, there are four significant figures in 0.8900
(c) when zeros are present in the beginning of a number, then it is never considered as significant figures.
For example: 0.042, here two significant figures.