KT1988
Landing Distance (LD) is the distance that you get out of the graph (assuming you do it right).
Landing Distance Required (LDR) is the distance you get after applying the various factors to the Landing Distance.
if you do an internet search for CAP698, you will get the workbook produced by the UK CAA. For many years students could take this into their exam, but this is no longer permitted. But the book explains a great deal about this subject, including how to use the graphs and how to do the calculations.
If you do an internet search for Difference between Landing Distance and Landing Distance Required, you will find lots of useful stuff on the subject.