Running load is a limitation that prevents floor damage.
It is given as kilogram per meter, kilogram per inch, or pound per inch. And 62 kg/in limit means that if we cut the aircraft fuselage in slices (the width of each is 1 inch) the total mass loaded in the slice cannot exceed 62 kg. The limit can be set differently in different areas of the aircraft. Usually, it is higher in the section over the wing and decreases in the AFT part of the aircraft.