The Decimal number system has following rules.
Suppose you have to write a number 4,567,892 .
2 -ones - (first period)
9-tens - (first period)
8-hundreds - (first period)
7-thousands - (second period)
6-ten thousand- (second period)
5-hundred thousand- (second period)
4-million- (third period)
then comes ten million,hundred million and then Billion.
If a number is given you have to apply commas from left to right after every three places.
So, your number is 9,418.
8-first period
1--first period
4--first period
9- second period