Cathay Boy: was this from a downgrade (e.g. PE --> Y - PE miles, US$40 and upgrade cert)?

If yes, can the upgrade cert mileage exceed the mileage from which the cert was earned (e.g. obtained cert from HKG-BKK PE-->Y , use on HKG-JFK Y-->PE)?
Also must it be same class as original flight (e.g. go from HKG-JFK PE-->J in example above)?