You know, this is really a lost exercise?
There is a story about James Mitose, 15th dan.
You ask how can there be a 15th dan if there are only 10 dan ranking?
It seems that there was so much promotion within certain styles that practitioners were giving away dan ranking to be one up on the next guy, instead of letting the years pass with training and understanding a master should have.
Outraged at the hollow promotions, James Mitose told these other teachers that he should 15th dan if they thought they were 7th or 8th dan. In my old encyclopedia of martial arts, it shows James Mitose, 15th dan ... unlike my new book which is a list of tournament winners over the years, and no dan ranking for past masters.
This line of who is a higher dan, or who has been promoted to a higher dan rating is a lost cause. It doesn't help you to understand your training, nor is it relevent to your personal journey ... unless you wish to have the ego of saying you have trained under a teacher of a certain dan rank as a measure of your own accomplishments, which also is ego.
Let it go ... or find out for yourself to satisfy your own curiosity. But asking for answers without confirming them, or knowing how to confirm them is a hollow, worthless journey.
Now go find the lineage and then comeback ... at least we will have something to talk about.