I received a security warning

I use WordFence for security and they just issued me the following warning about my site, http://www.mindingtherapy.com.

Warnings:

* Modified plugin file: wp-content/plugins/wp-super-cache/wp-cache-base.php
* Modified plugin file: wp-content/plugins/wp-super-cache/wp-cache.php

I don’t know what this means or what I’m supposed to do about this. Can anyone help me?

http://wordpress.org/plugins/wp-super-cache/