In a number, to determine the number of significant figures following 3 rules are used:
(1) The digits which are non-zero are always significant.
(2) Any zeros between two digits which are non-zero are significant.
(3) In the decimal portion, trailing zeros are significant.
The number is 0.0032 nm, it has two non-zero digits and the zeros are not trailing zeros.
Therefore, there are only 2 significant figures (underlined): 0.0032.
