  The existence probability $E_p$ and the percolation probability $P$ of the
bond percolation on rectangular domains with different aspect ratios $R$ are
studied via the mapping functions between systems with different aspect ratios.
The superscaling behavior of $E_p$ and $P$ for such systems with exponents $a$
and $b$, respectively, found by Watanabe, Yukawa, Ito, and Hu in [Phys. Rev.
Lett. \textbf{93}, 190601 (2004)] can be understood from the lower order
approximation of the mapping functions $f_R$ and $g_R$ for $E_p$ and $P$,
respectively; the exponents $a$ and $b$ can be obtained from numerically
determined mapping functions $f_R$ and $g_R$, respectively.
