Domain root dulication

Im having an issue with the redirect.
When I enter the target url as the following
http://www.tattoos-hurt.com/category/tattoo-articles/
when I try to go to the url that I want directed to that target it takes me too the following
http://www.tattoos-hurt.com/http:/www.tattoos-hurt.com/category/tattoo-articles/
If I change the target url to the following
/category/tattoo-articles/
then when I test the redirect it just takes me to /category/tattoo-articles/.
Why is it when I enter the root it puts it in twice and when I leave it out, it dosent put it in at all?

http://wordpress.org/extend/plugins/redirection/