  After the theoretical prediction that SmB$_6$ is a topological Kondo
insulator, there has been an explosion of studies on the SmB$_6$ surface.
However, there is not yet an agreement on even the most basic quantities such
as the surface carrier density and mobility. In this paper, we carefully
revisit Corbino disk magnetotransport studies to find those surface transport
parameters. We first show that subsurface cracks exist in the SmB$_6$ crystals,
arising both from surface preparation and during the crystal growth. We provide
evidence that these hidden subsurface cracks are additional conduction
channels, and the large disagreement between earlier surface SmB$_6$ studies
may originate from previous interpretations not taking this extra conduction
path into account. We provide an update of a more reliable magnetotransport
data than the previous one (Phys. Rev. B 92, 115110) and find that the
orders-of-magnitude large disagreements in carrier density and mobility come
from the surface preparation and the transport geometry rather than the
intrinsic sample quality. From this magnetotransport study, we find an updated
estimate of the carrier density and mobility of 2.71$\times$10$^{13}$
(1/cm$^2$) and 104.5 (cm$^{2}$/V$\cdot$sec), respectively. We compare our
results with other studies of the SmB$_6$ surface. By this comparison, we
provide insight into the disagreements and agreements of the previously
reported angle-resolved photoemission spectroscopy, scanning tunneling
microscopy, and magnetotorque quantum oscillations measurements.
