Appraisal results only apply to the organizational unit appraised and typically not to the whole company. (Large organizations are not usually appraised as an entire enterprise.) A CMMI appraisal could be for an organization, department, or single project. There isn’t a preset number of projects required to be assessed by CMMI appraisal methods. The business needs for process improvement drive the requirements for an appraisal, and therefore, a single project or work group could be driving the appraisal requirements. These are tailoring options available to you as you develop your appraisal plan with your lead appraiser. An appraisal determines an organizational unit's process capability at a point in time and applies to the part of the organization defined as the “organizational scope.
Ultimately, any appraised entity receives an Appraisal Disclosure Statement (ADS) and a Final Findings Report from their lead appraiser. These forms not only document the achieved maturity level or capability level profile, but also document which parts of the organization were appraised. These reports are owned by the sponsoring organization and lead appraiser. They do not come from the CMMI Institute.
You may want to review the Executive Summary section of the SCAMPI Method Definition Document (MDD). This describes the method used by lead appraisers and would probably help you prepare for an appraisal by knowing what to expect.