Additional self-signature

[Oskar L.]

Hello, I'm new on this list. Can anyone tell me why I get a second
self-signature when I do this:

oskar at MM2:~$ gpg --list-sigs
/home/oskar/.gnupg/pubring.gpg
------------------------------
pub   1024D/7EE6D97F 2005-05-18
uid                  foobar <foo at bar.com>
sig 3        7EE6D97F 2005-05-18  foobar <foo at bar.com>
sub   4096g/E53284D9 2005-05-18
sig          7EE6D97F 2005-05-18  foobar <foo at bar.com>

oskar at MM2:~$ gpg --export -a --output public.asc foobar
oskar at MM2:~$ gpg --export-secret-key -a --output secret.asc foobar
oskar at MM2:~$ rm -f /home/oskar/.gnupg/*
oskar at MM2:~$ gpg --list-sigs
gpg: keyring `/home/oskar/.gnupg/pubring.gpg' created
gpg: /home/oskar/.gnupg/trustdb.gpg: trustdb created
oskar at MM2:~$ gpg --list-sigs
oskar at MM2:~$ gpg --import secret.asc
gpg: keyring `/home/oskar/.gnupg/secring.gpg' created
gpg: key 7EE6D97F: secret key imported
gpg: key 7EE6D97F: public key "foobar <foo at bar.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1
oskar at MM2:~$ gpg --import public.asc
gpg: key 7EE6D97F: "foobar <foo at bar.com>" 1 new signature
gpg: Total number processed: 1
gpg:         new signatures: 1
oskar at MM2:~$ gpg --list-sigs
/home/oskar/.gnupg/pubring.gpg
------------------------------
pub   1024D/7EE6D97F 2005-05-18
uid                  foobar <foo at bar.com>
sig 3        7EE6D97F 2005-05-18  foobar <foo at bar.com>
sig 3        7EE6D97F 2005-05-18  foobar <foo at bar.com>
sub   4096g/E53284D9 2005-05-18
sig          7EE6D97F 2005-05-18  foobar <foo at bar.com>