PCI-E 3.0 problem

My video card report read - "Video Bus: PCIe v3.0 x16 (8.0 Gb/s) @ x16 (8.0 Gb/s)"

Why is it at 8 Gb/s? 

PCIe 3.0 x16 should be 16Gbytes (not sure if my report suggest that i am at abysmal 8 gigabits=1gigabyte effective???

Thanks for all the help.