\d{3}a digit, repeated exactly 3 times
?repeats the group contents below at most once:
-the literal - (4510 / 558 / 2D16)
\sany whitespace character
\.the literal . (4610 / 568 / 2E16)
\d{3}a digit, repeated exactly 3 times
\1?optionally matches the text saved by group 1
\d{4}a digit, repeated exactly 4 times
g modifier: global. Finds all matches instead of stopping after the first