pip is £62.25 per week and the contracts are calculated using that figure as the majority are on that.
wpms is £69.50 per week so over a contract you would pay more so they reduce the ap for wpms, but it means if you extend the contract you would be paying £7.25 too much hence the refund, why they cant just take less from the war pension i dont know, is another of those wierd things in the world that is motability.