Help needed with Comcast fiber and multiple site connections

Hello, we have just had Comcast fiber installed and I don't understand the ip assignments I was given by Comcast. Here is what they sent me:

WAN Block:

Link IP Address: 50.x.x.16/29

Gateway: 50.x.x.17

Layer 3 IP: 50.x.x.17 - 50.x.x.22

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LAN Block:

Everything is listed as N/A

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Layer 3 Subnet Mask: 255.255.255.248

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The setup is Comcast Metro-E EDI at our main site and Comcast Metro-E EPL at the other sites, so I don't think they have direct internet access and must go through our main site to get out to the internet.

I have our Sonicwall TZ300 configured at the main site, that was easy enough, but I'm not quite sure how to set up our other sites. Do I assign the WAN ip on the router at each site to be an ip that is within the LAN scheme of our main site, and use the given gateway address of 50.x.x.17 at each site? I could use some advice on how to connect and route our other sites to and through the main site, thanks everyone.