surface book charger

I'm utterly confused, my Surface Book 1 has a 1625 charger, which is 12 volts 2.58 amps with 36 watts. I'm seeing everywhere I can run a 15 volt 6.33 Amp charger on this model when I'm looking to buy a car charger for my surface, they all list my model as capable of running their 15 volt...