Hard to know what you're describing here, of if there's a question. What was the nature of your concussion, and the subsequent treatement? Did you get a CT scan at the time which may have revealed a bleed?
Who is guiding you through this process?
When you say you gave your medical records to "the doctor," which doctor? Your AME? If the FAA is moving for a special issuance here (lots of information not being given), then the FAA will need all the records provided to your AME, and more. The bottom line is that the FAA will require whatever they require, and you'll need to provide it. Before you invest so deeply in this event, you should make sure you have adequate counseling and guidance. Hopefully you're not doing all this on your own.
At the time of your injury, did you have post-traumatic amnesia, or an altered state of consciousness?
Review the FAA Aviation Medical Examiner's Guide table on head injury:
https://www.faa.gov/ame_guide/media/Head-Injury.pdf
Also review the AME Guide for a Neurologic Evaluation.
https://www.faa.gov/ame_guide/media/NeurologicalSpecificationSheet.pdf
Note that the FAA calls for all prior records, physicians notes, etc.
Did you have, or have you had a cardiac issue that would have required a cardiac catheterization?
It's unclear if you're being requested out of the blue to do a cog screen now for something that happened eight years ago, or what the circumstances are around your prior injury, or why it's an issue now.
If you look at the first table linked, you'll see that item C has a five-year waiting period, and that can be due to something as small as a very, very tiny bleed discovered in a CT scan following a concussive event. It may be due to a severe head injury with amnesia, altered state of consciousness, of loss of consciousness.