The iqn in the "General Properties" is the ESXi host's iqn (not the one for the NAS box) and you should not edit it unless there's a special requirement to do it. What you need to do is to register the ESXi host with the generated iqn on the storage system and present the LUNs. On the ESXi host, you should only need to enter the target's IP address in the "Dynamic Targets" tab.
André