Significant figures are all the digits excluding leading zeros for small decimals and zeros at the end of an integer.
45.030 has 5 significant figures because the zero at the end is after the decimal point. This means that the number was measured with 3 decimal places of precision. If the last zero was not significant, the number would be written 45.03.
On the other hand, 45030 only has 4 significant figures. Hope this helps!
