The overall visibility score is based on a compilation of all sections of the report. It includes all the directories, data aggregators, local pages, and voice search. If the business is missing any of these listings or if any of the NAP information is different than what was provided in the edit client page it can keep the score from reaching 100%. Keep in mind that if you did not order a specific service we may not be managing all listings and could be why they are not showing in reporting and hindering the score.