Ok. I'm trying to make the left look like the right. I'm kinda lost here. Suggestions?

\documentclass{article}
\usepackage{tikz}
\usepackage[margin=0.5in]{geometry}
\pagestyle{empty}
\begin{document}
%\input{../tikz-setup.tex}
\usetikzlibrary{shapes, arrows, calc, positioning, matrix }
% Define block styles
\tikzstyle{line} = [ draw, -triangle 45 ]
\tikzstyle{list} = [ rectangle, draw,
minimum width = 6em
]
\tikzstyle{ptr-box} = [ rectangle,
text width = 8em
]
\begin{center}
\begin{tikzpicture}[align = flush center, font = \small]
% Place nodes
\matrix [matrix of nodes, row sep = 0em] (age)
{
|[list] (free)| Free Page \\
|[list] (free2)| Free Page \\
|[list] (pg6)| Page 6 \\
|[list] (pg12)| Page 12 \\
|[list] (pg4)| Page 4 \\
|[list] (pg8)| Page 8 \\
};
\matrix [matrix of nodes, row sep = 0em,
left = of age,
nodes={text width=6em},
matrix anchor = north east,
] (ptr) at (age.north west)
{
|[ptr-box, ] (oldest)| \textbf{oldest\_ptr} \\ \tiny{Points to pool of free pages.} \\
|[ptr-box] (oldest-valid)| \textbf{oldest\_valid\_ptr} \\ \tiny{Points to oldest vaild cache page, else NULL if cache is empty.} \\
|[ptr-box] (newest)|\textbf{newest\_ptr} \\ \tiny{Points to newest vaild cache page.} \\
};
% Draw edges
\path [line] (oldest) -- (free);
\path [line] (oldest-valid) -- (pg6);
\path [line] (newest) -- (pg8);
\end{tikzpicture}
\end{center}
\end{document}


