is this USCIS computer glitch or what?

Recently I received the same confirmation emails from USCIS multiple times, with different dates. Is this normal or should I contact USCIS to confirm it?

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*** DO NOT RESPOND TO THIS E-MAIL ***
The last processing action taken on your case
Receipt Number: xxxxxxxx
Application Type: I485 , APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS
Your Case Status: Card/ Document Production

On November 14, 2012, we ordered production of your new card. Please allow 30 days for your card to be mailed to you. If we need something from you we will contact you. If you move before you receive the card, call customer service at 1-800-375-5283.

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*** DO NOT RESPOND TO THIS E-MAIL ***
The last processing action taken on your case
Receipt Number: xxxxxxxx
Application Type: I485 , APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS
Your Case Status: Card/ Document Production

On November 10, 2012, we ordered production of your new card. Please allow 30 days for your card to be mailed to you. If we need something from you we will contact you. If you move before you receive the card, call customer service at 1-800-375-5283.