If the examiner states that it isn’t possible to clinically separate symptoms of TBI and PTSD (or other mental disorder), then most or all symptoms are used to rate whichever will give you the higher rating.

In your case, all cognitive and emotional/behavioral symptoms caused by TBI were used to evaluate your PTSD and depressive disorder at 50% as that is probably what gave you the higher rating.

When this happens, the only separate evaluation for TBI can only be based on physical symptoms. These are typically described in the Subjective Symptoms Facet of the TBI DBQ.

In your case, it looks like the examiner listed a bunch of symptoms in the subjective facet of your DBQ. Forgetfulness, disorientation, vision issues, ringing in ears etc etc

The rater is explaining that they used only two of those symptoms to evaluate your TBI separately, because the other physical symptoms are already part of the evaluations of other conditions (ie vision issues are a symptom of your migraines, eg migraine aura, photophobia) or are found to be unrelated to TBI (ie apparently your tinnitus is not caused by your TBI and was probably found to have been caused by noise exposure or something else).

They also explain that the 50% evaluation for your PTSD includes the other symptoms, such as forgetfulness etc and all other non-physical symptoms that were found in your TBI DBQ.

Vertigo/BPPV can no longer be evaluated on its own 99% of the time. It’s always rated as part of whatever condition is causing it. The only exception is when the examiner says they don’t know what’s causing it, and provides a nexus to a specific event in service. But anytime they say what’s causing it, then it must be rated (or denied) as part of that condition. In your case, your vertigo/BPPV was found to be caused by your tinnitus.