  Let $J_r$ denote a full $r \times r$ Jordan block matrix with eigenvalue $1$
over a field $F$ of characteristic $p$. For positive integers $r$ and $s$ with
$r \leq s$, the Jordan canonical form of the $r s \times r s$ matrix $J_{r}
\otimes J_{s}$ has the form $J_{\lambda_1} \oplus J_{\lambda_2} \oplus \dots
\oplus J_{\lambda_{r}}$ where $\lambda_1 \geq \lambda_2 \geq \dots \geq
\lambda_{r}>0$. This decomposition determines a partition
$\lambda(r,s,p)=(\lambda_1,\lambda_2,\dots, \lambda_{r})$ of $r s$, known as
the \textbf{Jordan partition}, but the values of the parts depend on $r$, $s$,
and $p$. Write \[(\lambda_1,\lambda_2,\dots,
\lambda_{r})=(\overbrace{\mu_1,\dots,\mu_1}^{m_1},\overbrace{\mu_2,\dots,\mu_2}^{m_2},\dots,
\overbrace{\mu_k,\dots,\mu_k}^{m_k}) =(m_1 \cdot \mu_1, \dots,m_k \cdot
\mu_k),\] where $\mu_1>\mu_2>\dots>\mu_k>0$, and denote the composition
$(m_1,\dots,m_k)$ of $r$ by $c(r,s,p)$. A recent result of Glasby, Praeger, and
Xia in \cite{GPX} implies that if $r \leq p^\beta$, $c(r,s,p)$ is periodic in
the second variable $s$ with period length $p^\beta$ and exhibits a reflection
property within that period. We determine the least period length and we
exhibit new partial subperiodic and partial subreflective behavior.
