Black Lion Audio PBR8 8 Slot 500-series rack with Built-in Patch

I see this on some of the most popular 6-slot racks; API 500-6B, RN R6, Radial SixPack I imagine the answer is staring me in the face but

6-slot 500 Series Chassis with LED Current Consumption Meter Channel 7-8 Thru Conversion: Channels 7-8 can be used to convert signals

8 slot toaster Why is there IO for Channels 7 and 8 if the R6 only holds six modules? Channels 7 & 8 do not correspond to module slots, so the connectors are made

88cash slot 1 Rupert Neve Designs R6 · 2 API 500V · 3 Cranborne Audio 500R8 · 4 Lindell Audio 510 · 5 Radial Engineering Workhorse 8-Slot 500 Series