question about code chapter 2 07_lsp and 08_lsp

hi, 
why is fuel_capacity argument assigned to 2 properties?

class Vehicle:
    def __init__(self, fuel_capacity: float):
        self._fuel_capacity = fuel_capacity
        self._fuel_level = fuel_capacity


class PowerSource(ABC):
    def __init__(self, capacity: float):
        self._capacity = capacity
        self._level = capacity