The graphics card should be in the top PCI-Ex16 slot. With no other cards installed, GPU-Z *should* report the card running at x16. Specifications for your board
clearly states the two PCI-Ex16 slots should run at x16/x0 for a single card solution and x8/x8 with two cards installed.
Assuming your graphics card is installed in the top PCI-Ex16 slot, what slot are you using for your AVerMedia card?