To elaborate, because canards are really interesting, they deliberately create a vortex in a very strategic position.
Assuming it's fitted the right way up lol, the direction of rotation will be "into" the door. When done well, this helps the airflow around the side of the car "stick" to the body rather than separate & prevents air from "spilling out" of the flat floor around the side skirts (hence maximises the diffuser).
A little bit of aero balance can be gained (slightly balances a rear wing) but that's a mere "nice benefit" compared to maximising a 3m x 1.5m flat floor....