(?m)applies the following effective flags to the remainder of the pattern: m m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string
^start of line
\d{4}a digit, repeated exactly 4 times
-the literal - (4510 / 558 / 2D16)
\d{2}a digit, repeated exactly 2 times
-the literal - (4510 / 558 / 2D16)
\d{2}a digit, repeated exactly 2 times
:the literal : (5810 / 728 / 3A16)
.*any character (except for line terminators), repeated any number of times
\zend of string