Fix Unexpected Partition Drive (M1 chip)

That is completely normal (sort of). It seems you have renamed your data volume in a way that did not sync with the system volume (probably from the Finder). Use Disk Utility to rename the "Untitled - Data" volume to "MacBook - Data" or any other name to replace the "Untitled" part of "Untitlted - Data" making sure to leave the " - Data" part as is. If you rename it to something other than "MacBook - Data", then the change should also affect the name of the "MacBook" volume. For exampel if you rename "Untitled - Data" to "Macintosh SSD - Data", then the "MacBook" volume should be automatically renamed to "Macintosh SSD - Data". Personally I would keep the base names of these two related volumes the same to avoid confusion if any other APFS volumes are created.

Beginning with Catalina macOS now has a read-only system volume with a default name of "Macintosh HD" and a read+write volume containing your home user folder(s) with a default name of "Macintosh HD - Data". macOS tries to hide this separation from the user, but unfortunately macOS is partially broken when renaming the "Macintosh HD" volume from within the Finder (again macOS hides the " - Data" part from the user).

https://support.apple.com/en-us/HT210650

Edit: I think you need to right-click or control-click on the "Untitled - Data" item on the left pane of Disk Utility to get an option to rename the volume.

While the mismatched names will work, it does make it confusing. Looks like the volumes a named match set again. If you want to rename it again it is best to do so through Disk Utility again until macOS fixes the volume renaming issue when renaming the volume from within the Finder.