Docs improvement: what do the colons mean? ":"

[vladinator1000]

I was reading the vocabulary docs and saw this example

number -> [0-9]:+

What do the colons and plus mean?

[DenverCoder1]

:+ is Kleene plus from Regular expressions meaning "appearing one or more times"

:* is Kleene star meaning "appearing zero or more times"

[TekuConcept]

:? - "appearing zero or one times"