Fragmentation % Discrepancy?

I just ran a disk fragmentation analysis with the most current version of Defraggler and it showed 11% fragmentation. I immediately then ran an analysis with the most current version of Auslogics Disk Defrag and it showed 5% fragmentation. Why the big discrepancy?

Very possibly the Defraggler % includes System Volume Info, that best measure of fragmentation % is not as obvious as it first apperas, the Windows Defrag shows much lower than Defraggler to, suggestion on this is here Less Strict Fragment Defintion, Display & Reporting End users are confused by high fragmentation % and many red blocks

3rd party Defraggers have an incentive to be pessimistic, to appear more beneficial (compare with noisy personal firewalls in security field).