It probably means what it says: incorrect password. On the other hand, this dangerous (imho) tutorial has you editing /etc/passwd by hand so it's also possible you made a mistake in editing it, or their hand-done changes are incorrect or incompatible with your login system. It's better to use usermod to change a users' setup...

One thing I don't see it doing is adding the login wrapper to /etc/shells, if /etc/shells exists on your system it's probably necessary to add it.

Be sure to complete all steps of the tutorial, including the changes to sudoers.