Because the IP configuration doesn't actually set the IP of the module. The actual IP is set with Bootp and then made persistent with either the internet tab (your second image) or RSLinx or the web interface if available on the module. The configuration IP doesn't have to match for the module to actually work. You can still connect through it via RSlogix5000. Best practice to set the configuration IP to match however, as any remote modules that reside in the IO tree as children will likely have the same IP octets.