Two countries same name?

When I look at the Visitor Countries in my stats I see “United Kingdom” and “Great Britain” both with the Union Jack in front of them. Is there a reason for having both the United Kingdom and Great Britain?

I’m not an expert in geographie, but

United Kingdom of Great Britain and Northern Ireland is known as United Kingdom (UK).

So Great Britain is United Kingdom without Northern Ireland.

In the other direction:
If access from Great Britain is shown separat, I guess that UK is access from Northern Ireland. Right?

Regards,
Christian.

http://piwik.org/faq/troubleshooting/#faq_65