What does channel 7 and 8 on a 6-slot 500 series rack do?

What does channel 7 and 8 on a 6-slot 500 series rack do? 8 slot 500 series rack Description Standing for Music Compact Mixer 8, the MCM-8 is an 8 slot 500 Series enclosure with 10 channel mixing capabilities and it´s the Top of the Line of 8020 t slot The Music People B2B This is 8 Slot 500-Series RackPatchba from Converters produced by Black Lion Audio

8020 t slot Description Standing for Music Compact Mixer 8, the MCM-8 is an 8 slot 500 Series enclosure with 10 channel mixing capabilities and it´s the Top of the Line of

88 fortune slot 500 Series Heritage Audio MCM-8 II Summing Mixer $2, Add to wishlist Quick View OUTBOARD Heritage Audio OST-10 10-Slot 500 Series Rack $ 500 Series Chassis · Mercury G810 Rack System 1 wPSU · Mercury G810 Rack System 2 wPSU · API 500-8B 8 Slot Lunchbox · BAE 500 Series 11 slots + PSU · BAE 500