APA Style has a very simple guideline for leading zeros: If a value has the potential to exceed 1.0, use the leading zero. If a value can never exceed 1.0, do not use the leading zero.

Are leading zeros necessary?

3. Leading zeros are NOT significant. They're nothing more than "place holders." The number 0.54 has only TWO significant figures. 0.0032 also has TWO significant figures.

Did adding leading zeros affect the number?

No matter how many zeros you add on to the beginning of the number 27, it doesn't change. Zeros attached to the beginning of a number in this way are called leading zeros. In decimals, this idea of zeros that don't add value to a number can be extended to trailing zeros.