回复：Letter from USCIS, what does it mean? hard to say

if it's address change, it generally will say so on in the letter, the reference number for the calling.
your letter is ambigious as to what it is about.
but you may use it as a proof if your address change was not updated by USCIS.
always ask for the agent's number and reference number if you make a phone call to USCIS for address change.