How to access class variable? instances vs class

[drSlump]

Hello everyone, I am learning OOP in python, specifically class variables. It is clear to me what they are, but I do not get why they should be accessed through the instance. Referring to the following tutorial in the method apply_raise the variable can be accessed through the instance (line 15 --> self.pay = int( self.pay * self.raise_amount )). I tried to access the variable through the class (line 16 --> self.pay = int( self.pay * Employee.raise_amount ), and it works in the same way, at least it looks so to me. Is there any difference?

class Employee:

    raise_amount = 1.04

    def __init__(self ,first ,last ,pay ):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first+"."+last+"@company.com"

    def fullname(self):
        return "{} {}".format(self.first, self.last)

    def apply_raise(self):
        self.pay = int( self.pay * self.raise_amount )
       #self.pay = int( self.pay * Employee.raise_amount )
        return self.pay