If a power supply has 2 different powers which one is used?

The Nintendo switch power supply has a voltage of 5V and 1.5 A / and 15V with 2.6 A. This corresponds to 7.5 watts and 40 watts. The Samsung galaxy S20 ultra can be charged with a maximum of 48 watts. If I charge the cell phone with the Nintendo Switch power supply unit, will it be charged with 7.5 watts or with 40 watts? Can you also set what power the power supply outputs?

Then you see that

The highest possible

Depends on your cell phone.

The switch uses USB C with power delivery.

If your cell phone supports power delivery, it charges with 48W, if it does not support it with a maximum of 7.5W and if your cellphone does not recognize the power adapter as a USB wall charger, then with 0.5W or 2.5W if it assumes that the USB port can deliver it.