This option has been included for members to lock in their Rally Registrations for less than the full amount.  You can also use it to pay down your Rally Balance before December.  Each purchase will be credited to your upcoming rally and an updated invoice will be sent letting you know your balance due.  NOTE: When your balance falls below $100, OR you are ready to pay your balance due, you can click on "EVENTS" tab on the left menu bar and make a final payment for your Rally balance.