You will need to ask the manufacturer of your hardness tester this question. I can only guess that it means LOAD, such as LD = 100 kgf for a Rockwell B test or LD = 150 kgf for a Rockwell C test.
The Equotip tester should have an in-built conversion to conventional hardness numbers - look at the menu screen where you can select material, direction and conversion.
The Equotip is a Leeb Hardness tester (see ASTM A956). Hence the L numbers are shorthand for Leeb. The subscript D indicates that the testing device is a D type (Equotip have many other types of devices including C , E and G ).