It's possible you're thinking of something else, like:

* The Moon's phase: The Moon goes through different phases, and you might be thinking of a specific phase number. However, there's no standardized numbering system for these phases.

* Lunar calendar dates: Some cultures use a lunar calendar, which tracks the cycles of the Moon. In this case, a "moon number" could refer to a specific date within a lunar month.

* A specific lunar event: Maybe you're thinking of a particular lunar event, like a lunar eclipse, and a specific number associated with that event.

Could you please clarify what you mean by "moon number"?