[CentOS] reposync

Hello,

During a reposync of the centos base mirror, how come there are more
packages downloaded than the iso file contains...

The iso's Packages directory contains 3956 rpm packages.
The reposync of base holds 6381 rpm packages.

This was done using centos's default yum repo file

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6