Domesday CountDir
The total file size will never, or very rarely, equate to the total size of the used sectors on any disc, because each file doesn't always take up a full sector. However, the total sector count calculated by CountDir is also incorrect by 120 sectors.
This would be due to the rounding involved in the VFS disc layout which uses actual sectors of &1800 bytes in LV-DOS, which are therefore equivalent of &18, or 24, ADFS or VFS sectors, although I can't quite get the numbers to add up here.