The copyright file contains the incomplete Debian packaging copyright boilerplate from older versions of dh_make. (C) alone is not considered a valid copyright notice in some countries. The word Copyright or the © symbol should be used instead or in addition to (C).

Copyright notices like this are, in any country that's a signatory to the Berne Convention, not required to claim copyright on a work, but their presence may allow claiming additional damages should a copyright case go to court. If you provide a notice, you may as well provide one that's legally recognized in a broader range of countries.