MFT region assignment phase is required to resolve issues associated with MFT fragmentation. Term "region" is used to describe single separate MFT fragment (it is used because "fragment" was already used for something else). This phase is fully automatic and you cannot interfere with the process. Assignment results are provided for reference only. Typical NTFS volume has up to 20 MFT regions, one of them being substantially larger than others. Percentage of unassigned MFT regions is also displayed. Some entries are always left unassigned, so one should not expect displayed value to be zero during normal operation. In general use, up to 5% unassigned entries should be considered acceptable.