(1) Right... if you prefer to have the ATA "downstream" of your router, i.e., a member of your LAN just like a PC, then you connect the WAN port of the GS ATA to a LAN port on your router.

(2) There are several issues if you elect to put the ATA upstream of your router. Here, the WAN port of the ATA connects to your cable/DSL modem and the LAN port of the ATA connects to the WAN port of your router.

U-Verse probably prohibits the upstream case (2).

With the ATA downstream (1), there are often port forwarding issues for some reason, with VoIPo. With two prior VoIP providers, this wasn't needed, in my case.

You may find many more U-Verse idiosyncrasies. I'm among those working to totally expunge AT&T from my telecommunications needs.