Distribution Media Format
A Floppy Disk Format normally has 18 Sectors per Track. But to technical advances there is actually enough Room on a Track to squeeze another 3 Sectors in. It also resizes the Clustersize to 4 Sectors per Cluster, shrinking the FAT-Size by two.
This has been known for years and also been used in different Programs like fdformat. When Microsoft started to distribute Windows 95 on Floppies they named that special Diskformat DMF and claimed to have invented it.