Rule 1: On the left side of the decimal point after every three digits give one space. If there is no decimal then after every three digits from left to right give on space and repeat till the complete data is written.
Rule 2: To the right side of the decimal point after every three digits give one space and repeat a space after every three digits till the data is complete.
Examples:
3714518730897.618530832 is not correct
3 714 518 730 897.618 530 832 is correct
55231647 not correct
555 231 647 correct
0. 54611 not correct
0.546 11 correct
1598.5409 is not correct
1 598.540 9 is correct
3745.10 is not correct
3 745.10 is correct