\documentclass[a4j,11pt,papersize]{jsarticle}
\usepackage{afterpage,graphicx}
\begin{document}

\newcommand*\checkcnt[1]{\texttt{#1} $=$ 
   \expandafter\the\csname c@#1\endcsname} 
\checkcnt{topnumber}\par
\checkcnt{bottomnumber}\par
\checkcnt{totalnumber}\par
\newcommand*\checkcmd[1]{\texttt{\string#1} $=$ #1}
\checkcmd{\topfraction}\par
\checkcmd{\bottomfraction}\par
\checkcmd{\textfraction}\par
\checkcmd{\floatpagefraction}

\renewcommand\topfraction{0.85}
\addtocounter{topnumber}{2}

\end{document}
