Mary Smith is seen by Main Street Medical. She has a $500 deductible. Mary Smith has met $450 of her deductible. Her insurance was billed a 99213 at $95. The insurance allowed $80 and paid $30.
In this case, Mary Smith has insurance but the amount the insurance company paid is irrelevant to this question. It is stated that she paid $450 of a $500 bill, so whatever the situation with the insurance, she should be billed for just the remaining $50.