How are grades shown in the ECTS grading table on LUC diploma supplements?

LUC uses a letter grading system (A to F). However in LUC grading tables, the numerical values of these letters are used instead. This means that grading tables on LUC diploma supplements show the distribution of grades in the range 1.7 (= C, the lowest passing grade) to 4.0 (=A/A+, the highest passing grade), rather than the standard Dutch passing grades of 6 to 10.