The number on the meter is the power coming from the brick to the charger, so that number is before the losses that come from wireless. So the phone isn't actually charging at 9w, that's just how much power is being used. My guess is the fake charger is likely a regular 7.5 watt charger with the magsafe stuff added around it.
Check for The Genuine Canon Hologram. Canon’s anti-counterfeiting hologram can be seen on replacement batteries, battery chargers, and camera grips packaging. If the similar hologram seen above
Oppo says, "Battery Health Engine is able to keep a battery at 80% of its original capacity after as many as 1,600 charge cycles, effectively doubling the lifespan of batteries under current
fyNlu.