PE 730 PCI Slots 6&7

Company just acquired a Dell PowerEdge 730.

I notice on Riser 3, there is only 1 expansion slot available (PCI Slot 6). Although there is a Slot 7 listed on the rear of the chassis, and a bracket in place for a card, there is no actual slot.

Is there another riser card I can purchase so I can get use of both PCI Slots 6 and 7?

Is there a reason why this riser omits the slot to accomodate the #7 slot?

thanks,

vin