Sometimes ZAR data recovery software may fail to detect certain volume parameters properly.
Typical scenarios include
The volume was reformatted to a different filesystem type and certain amount of data was saved to the volume.
In this case, ZAR may discard the old filesystem in favor of the new one.
The volume was reformatted to the same filesystem type but with a different cluster size.
Or, there are multiple virtual disk image files with the same filesystem types stored on the volume.
In this case, ZAR may fail to detect the correct cluster size or data location.
If you know exact parameter values, you can enter them manually.
This forces ZAR to discard the calculated values and use the values you provide instead.