The first stage of the wizard recovery is for the program to try and assess how full the disk. The routine to do this is to read 1000 sectors over the full range of the disk.  If any sector has the same contents as the previously read sector, the sector is treated as unused. This is important as many disks are initialised with a fixed pattern of data when they are first produced. The calculation displayed on the analysis screen then indicates how much of the disk has been used, at any one time. Thus it will count files that have been deleted, or moved when a disk was defraged. The result is very useful when the disk is indicated to be say 20% full as it indicates a fairlt empty disk.  A disk with 85% means that it has been used alot and it is possibe that there are, or have been many files on the disk.

The second stage is for the program to try and determine the files on the disk, including deleted files.  For FAT, CDs/DVDs a Full Recovery mode is used to scan the directories.  For NTFS, the mode used is the Recover from file entries, ie a scan of MFTs