Non-Capturing Group(?:\d\.)? ?repeats the group contents below at most once:
\da digit
\.the literal . (4610 / 568 / 2E16)
Non-Capturing Group(?:\d{1,3}\.)? ?repeats the group contents below at most once:
\d{1,3}a digit, repeated between 1 and 3 times
\.the literal . (4610 / 568 / 2E16)
\d{1,3}a digit, repeated between 1 and 3 times
,the literal , (4410 / 548 / 2C16)
\d{1,2}a digit, repeated between 1 and 2 times