third party with budget

my car was hit by one of the budget client, the lady promise to cover the cost as I do not have an insurance, i'm the third party, budget toll me for third party they don't pay full car value they pay only 60% and they are going to give me my car. I fell this is not fair, its their client how damaged my car, my car is a 2018 polo sedan, why are they not paying the full car value amount only 60%, I told the I want the a car with same miles, model and year and they refuse. kindly assist