It is probably just replacing those boxes on the original W-2 with the new information. They are only updating the boxes that changed.
If you already filed then it will not change your tax return, just keep it for your records. The propose to to supply the Social Security Administration with the correct data and they use the copy sent by the employer to do that.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
