Pin down this metric definition

Two teams report different numbers for the same metric name.

Turn the loose metric below into a definition nobody can interpret two ways.

Work through every decision the name leaves open:
- The population: who is included, who is excluded, and what happens to test accounts, internal users, refunded orders, and deleted records
- The event: which timestamp defines membership in a period, creation or completion or payment
- The period: calendar or rolling, which timezone, how partial periods are handled
- The denominator, if there is one, and whether it is measured over the same population
- Deduplication: what counts as one, per user or per session or per device
- Restatement: what happens when a past row changes

Produce a one-paragraph definition, then a bulleted list of explicit exclusions. Finally, list the three interpretations most likely to cause two teams to report different numbers, and state the ruling for each.

Metric:

Numbers and metrics. Pinning down what a metric means, what a report measures, and whether a surprising number is real.