Confused about Facebook portal lineup for 2nd gen

Facebook released a 10” and 8” 2nd gen portal? The 10” has a usb port on a back. The 8” does not and has a power adapter which plugs directly into the portal?

I think I got a 8” off eBay which was advertised as 10”. There’s no usb on the back. I think the 8” usb port is under the speaker grill.