What is the difference between long sleeves (sleeve length 5) and extra long sleeves (sleeve length 7)?

Long sleeve John Miller shirts have a standard sleeve length 5. This means that de sleeve length is between 67 en 69 centimeters, measured from the shoulder. For tall men this is too short. They need a shirt with sleeve length 7. The sleeves are then seven centimeters longer than de standard sleeve length and the back is also extended.