  In this paper, we first give a new interpretation of Jimbo's boundary
condition for the generic Painlev\'e VI transcendents, as the shrinking
phenomenon in long time behaviour of the Jimbo-Miwa-Mori-Sato equation with
rank $n=3$. We then interpret Jimbo's monodromy formula from the viewpoint of
the isomonodromy deformation with respect to irregular singularities.
