What am I doing wrong with toppings?

So the amount of perfect toppings is 18 but every time a customer asks for 4 toppings, I end up putting 5 of two toppings and 4 of the other two since there is no possible way to put an equal amount of each toppings on the pizza. The customer always says that some toppings are missing what am I supposed to do? The customer asked for olives, pepperonis, mushrooms and sausage. When I gave them this pizza they said it didn’t have enough pepperoni and I had to refund it. How do I do it right?