Can somebody tell me, what does it’s mean, please? I am confused. After two month from the interview

Congratulations .How long did you receive the approval letter? I checked the history record of my case on the official website of uscis, showing that the fee waiver and decision were mailed on the same day on April 11th, but I haven't received the letter yet, so I'm a little flustered.:(
 
Congratulations .How long did you receive the approval letter? I checked the history record of my case on the official website of uscis, showing that the fee waiver and decision were mailed on the same day on April 11th, but I haven't received the letter yet, so I'm a little flustered.:(
Thank you very much and congrats for you tooAfter this notification, I received the decision in approximately 2 weeks!
 
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