%?optionally matches the literal % (3710 / 458 / 2516)
\s*a Unicode whitespace character, repeated any number of times
\d+a Unicode decimal digit, repeated at least once
Non-Capturing Group(?:,\d+)? ?repeats the group contents below at most once:
,the literal , (4410 / 548 / 2C16)
\d+a Unicode decimal digit, repeated at least once
\s*a Unicode whitespace character, repeated any number of times
%?optionally matches the literal % (3710 / 458 / 2516)