While there is usually a small gap between when you place your order and the date of delivery, your rental term begins on date of delivery. This means that whatever gap there was between your initial payment and delivery there will be an equal gap at the end of your term between your final payment and when your term expires.
For example, if you place an order for a 12 month term on June 1st with a confirmed delivery day of June 8th you will pay for your first month on 6/1 and second month on 7/1. But your rental term begins on 6/8. Your final payment would be collected on 6/1 of the following year with your term ending on 6/8 of the following year.