So let me guess... You filed N-400 and received biometrics reuse notice first, then you got receipt for filing N-400 explaining that your GC expiry is extended by 24 months...
The letter starts with "Thank you for submitting your application, petition, or request. Our office is currently processing it."
So what you see is normal. Essentially USPS delivered letters in different order. There's nothing to worry about.
Of course, anybody who got their biometrics reused may get biometrics appointment letter if reuse was sent in error.
Based on what you got so far, there's nothing to worry about. You received two letters as you should have, just in different order.
And one more thing: if you are a person who worries a lot, save your nerves, don't pay any attention to estimated processing times or steps on MyProgress bar. This is know to update a lot with various inaccurate estimates or dissapear altogether.
If you filed this month (December 2024), please join this group:
You'll be able to see other people's experiences who filed around same time as you.