Answer:
This can be because our number, 300,684, has only four digits different than zero.
Then we can write this number as:
300,684 = 300,000 + 600 + 80 + 4.
So we add only 4 terms.
So when we write a number in this form, we will have the same numbers of terms in the addition that the number of digits different than zero in our original number.