Repair APFS 'warning: overallocation detected on Main device'

gistfile1.txt

1. Boot into Recovery mode (by pressing CMD+R while boot macOS)

2. Unmount APFS volumes automaticaly mounted by Recovery (where /dev/disk2 is your APFS container)

    $ diskutil unmountDisk /dev/disk2
    Unmount of all volumes on disk2 was successful
  
3. Unlock APFS volumes (in case FileVault enabled for this volume)

    $ diskutil apfs unlockVolume /dev/disk2s1 -nomount
    Passphrase: <enter password here>
    Unlocking any cryptographic user on APFS Volume disk2s1
    Unlocked but did not mount APFS Volume

3.1. To verify that volume unlocked (look for "Yes (Unlocked)"):

    $ diskutil apfs list
    ...
    |   +-> Volume disk2s1 73D0148D-36A2-429D-AE11-8FFB7E89EED7
    |   ---------------------------------------------------
    |   APFS Volume Disk (Role):   disk2s1 (Data)
    |   Name:                      BigSur - Data (Case-insensitive)
    |   Mount Point:               Not Mounted
    |   Capacity Consumed:         349155135488 B (349.2 GB)
    |   Sealed:                    No
    |   FileVault:                 Yes (Unlocked)
    ...

4. Run APFS repair command

    $ fsck_apfs -oys /dev/disk2
    ...
    warning: overallocation detected on Main device: (0x128e04+1) bitmap address (0x7c93d)
    Fix overallocation (0x128e04+1) bitmap address (0x7c93d)? YES
    ...
    ** The volume /dev/disk2 appears to be OK.

Thanks for this! Helped me get back 200GB ❤️

Thanks for the guide!
It gave me the possibility to reformat my hdd to secure my 5-booting drive!