PCIE x16 slot only running my RTX 3080 at x4 (8GTs

PCIE x16 slot only running my RTX 3080 at x4 (8GTs pciex16 slot There're two x16 slot in the board In the first slot using GPU and working fine Now I try to put avermedia GC573 capture card in the second pciex16 slot configuration MOBO and GPU compatibility warning One additional PCIe x16 slot is needed

pciex16 slot configuration There're two x16 slot in the board In the first slot using GPU and working fine Now I try to put avermedia GC573 capture card in the second

lotus flower slot PCIe X16 Cable Graphics Card Support GPUs no more than 140 x 325mm GPU Slot GPU 140×325×25 CPU Maximum Height 88mm GPU Slots GPU But can you plug that card into a PCI-Ex16 slot AND have it work? Or My motherboard has PCIe x16 I also have