If I understand what you did, you connected a 65A (max capability) battery charger to your Macan, and turned ON the ignition, with the engine OFF, like you would during coding. And you then measured the current from the charger, with your clamp-on meter on the charger wire, and observed 19.4 Amps.
If this is what you did, your conclusion that you need to supply at least 19.5 Amps during coding is not correct. Depending on the charger output voltage, it was supplying more amps to charge the car battery than what is required during an "ignition ON, engine OFF" scenario. To measure how much current you need to supply during a coding session (ignition ON, engine OFF), just put your clamp-on ammeter on the pos or neg cable at the battery. No external charger or power supply should be connected.
Assuming that the radio, and the HVAC blower are off, and all lights are off, the ignition ON/engine off "idle" current is probably between 3 to 8 amps (my guess).