Trying to Port Forward dedicated Garry's Mod server.

Okay so I have port-forwarded my dedicated garry’s mod server before but i deleted the settings in the router page, and I have trouble doing it again. I know the port: 27015. I have a modem connected to a router (basement to upstairs). The modem is a cisco, and my router is an Asus Dual Band. I made my ip static on my Asus router. On my Cisco modem, whenever I port forwarded the ports 27015 and add my computers ip it says that it is invalid. I am not sure whats the issue. Also, when trying to add a static ip to the modem it doesnt show up.
Here are some pictures.

Thanks in advance!
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