  Let $\tilde{Q}$ (resp. $Q$) be an extended exchange (resp. exchange) cluster
quiver of finite mutation type. We introduce the distribution set of the number
of arrows for $Mut[\tilde{Q}]$ (resp. $Mut[Q]$), give the maximum and minimum
numbers of the distribution set and establish the existence of an extended
complete walk (resp. a complete walk). As a consequence, we prove that the
distribution set for $Mut[\tilde{Q}]$ (resp. $Mut[Q]$) is continuous except the
exceptional cases.
  In case of cluster quivers $Q_{inf}$ of infinite mutation type, the number of
arrows does not present a continuous distribution. Besides, we show that the
maximal number of arrows of quivers in $Mut[Q_{inf}]$ is infinite if and only
if the maximal number of arrows between any two vertices of a quiver in
$Mut[Q_{inf}]$ is infinite.
