  The investigation about the volume of a black hole is closely related to the
quantum nature of the black hole. The entropy is a significant concept for
this. A recent work by Majhi and Samanta [Phys. Lett. B 770 (2017) 314] after
us presented a similar conclusion that the entropy associated with the volume
is proportional to the surface area of the black hole, but the proportionality
coefficient is different from our earlier result. In this paper, we clarify the
difference and show that their calculation is unrelated to the interior of the
black hole.
