As others have said, the current PMP process is quite subjective. In my opinion, it’s not even intended to be a quantitative or numerically comparative tool.
My advice would be to focus on the intent of the ratings and what your supervisor is trying to communicate through them. Focus on the comments and what you’re doing well, and what you can improve.
A Valuable Contribution rating means exactly that - you’re making a valuable contribution to your team, stakeholders and the company. An Expects More indicates that there are some gaps you need to address. An Exceeds Expectations means you’re going above and beyond the requirements of your role and functional level.
Supervisors have autonomy to assign ratings as they desire, but they may be asked to provide a justification to their supervisor/s.
Don’t give too much thought about how you compare. It’s hard to compare against supervisors and teams.