Theme
Revenue
Revenue is an event with a defined shape: a price, a quantity, an optional product id, and optional receipt fields. The total is computed on ingest, not in the SDK — deliberately, so that one implementation of the arithmetic serves every language and no SDK can disagree with another about what a purchase was worth.
Send revenue from the server whenever the server is where the truth is. A browser that closes mid-request is not a reliable witness to a payment.
Per-SDK reference
Each page's §9 covers every field's meaning and where the total is computed.
React: use the browser client — see Browser §9.