Curious what this message means and if should be concerned or not.

I have been receiving the following message from the iThemes plug-in (Usually comes in spurts.....like 8 at a time....every so often)

Dear Site Admin,
A host, 64.15.155.158, and a user, , have been locked out of the WordPress site at http://delizios.com due to too many bad login attempts.
The host has been locked out until 2014-05-16 03:43:21 and the user has been locked out until .
To release the lockouts please visit the lockouts page.

Should this be anything to be very worried about? Or is just an informational message that indicates a hacker is trying to access our site......and that I shouldn't be too worried if I have the right security set-up?

Thanks for your feedback,
Bob