There are only 6 significant digits because in total there are 9 digits. We do not need the first 2 0's, so now we only have 7 digits. But the question is do we really need the last 0? The answer is no. No, you do not need the last 0 because we already know that it's .0049, and the 0 is just an extra.
So without all the insignificant 0's, the number would look like this:
