I'm having the same problem. The router doesn't work as the instruction manual states. When you click on the X next to offline computers it does not give the option to delete, it gives the option to add that computer to the block list. There is no way to edit the settings except for an online computer, and the reason I need to delete it is because it's not finding the computer.
I see it, too. I tried setting up static address for a Netgear router, hoping this would connect the gateway to the router (see my post of today). Also, don't you notice that it says "DHCP" and not "Static" after you've added the static address? What is this "offline" static assignment function for, anyway?
Although I do not use one of these gateways, it sounds to me like these are poorly worked instructions. My interpretation of them would be that this is the equivalent of a 'statis DHCP' function, when you can have the router associate a given IP lease within it's DHCP scope to a particular MAC address. The device you wish to have that IP should still use DHCP to obtain IP config information, but it will be given the same IP every time, and the IP will not be used by the router's DHCP server for anything else.
I may be wrong, but I do not beleive this is intended for use to record, or have the router recognize devices with true static IPs that do not get their IP address information via DHCP.
If I were setting up a second router on my LAN, that were connected to the main router, I would certainly not have it obtain IP config info via DHCP (even statically)...I would manually assign it for complete control.
As far as deleting the entries go, it seems from the manual, that the X in the 'online' entries provides the abiulity to block internet access to that devices, and the X in the offline entries provides the means to delete the entry.
Have you tried taking devices whose 'static' entries you want to remove offline so the router doesn't see them as online before trying to delete them?
Your interpretation of the DHCP/Static makes perfect sense! So much for thinking this might solve my (and other poster's) problem with SMC gateway not recognizing devices with static addresses. I thought this might force the "base" SMC to connect with my "repeater" router - not.
But, methinks you have the "X" delete function backwards. I think it is as the previous poster described. You can delete the onlines, but trying this with the offlines just allows it to be blocked. In both our cases, the static-addressed devices aren't connecting to the gateway anyway (which is why we tried it in the first place). I think the only way to get rid of the offlines is to push the button (reset)!
Since there is no solution posted, I thought I should let folks know how I got it to do what I wanted. If you click the "X" next to the item you'd like to change, you will then be asked if you want to Add this computer to Blocked Devices. Just click "OK". You'll be brought to the Parental Control > Managed Devices > Add Blocked Device screen. The item you are working with will be listed in the Custom Device section and it will be set to Always Block? Yes. Just click on save and your device will be added to the Always Blocked list (I know this is NOT what we have set out to do, but it'll all work out.) Once it is in the Always Blocked list, you can click on the X next to the device in this list and it'll ask if you want to delete the device from the Always Blocked list. Once you've removed it, you can then re-add it to the Static IP Devices with your new settings as if adding it for the first time.