Alert Question

Thanks for such an invaluable tool, Wordfence!

I received an alert that “a non-admin user” signed into my WordPress site. I am not sure what to make of that unless the password was hacked. Is that what it means? (Could it be that the alert is referring to a non-user signing in to comments or one of the lead capture tools?)

http://ww.wp.xz.cn/extend/plugins/wordfence/