THe following message was extracted from other site. It is helpful for someone who waits for the results of i-485
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My LUD on both my 104 and 485 changed twice. I asked my friend who works for the USCIS line and she looked into my cases. She said that everything looks normal and that it looks like some internal processing was done on both forms that did not produce any kind of outcome on the application. She said that this is normal and to not read much into it. She added that whenever the NSC does anything to any of your applications, they are required to change the Last Updated Date.