Let us consider the definition of distance and displacement so that we can have a better idea about the two situations
a) Distance is a scalar quantity and it signifies the overall ground covered by a n object irrespective of its direction, initial and final position
b) displacement is a vector quantity and it signifies how far the object moved from its original position.
now let us see the scenario with a pictorial representation (Figure 1)
Thus the greater displacement is by Runner A [maximum difference in ground cover from the start point ]
The greatest distance is by Runner B [covered the complete track]