My first comment is that if Dr. Chang, a neurosurgeon, looked at the MRI, and was unconcerned about the white matter, you should not be either. On my first MRI it was reported as "one or two focal areas of white matter hyperintensity involving the subcortical and deep white matter." The radiologists note this kind of stuff so that down the road, if something starts to change, they have a good reference. In your case, it means that someone reading your next MRI a year from now will see a white matter indication, then see that it was already observed previously, and if it hasn't changed, all is well.
SRT stands for speech recognition threshold, meaning the level of volume boost you need to recognize speech. I score around 60 db or so, meaning a hearing aid is in order for me. I think 10 or 15 db is pretty mild, and the difference between them is not significant either. Your speech recognition number of 48% is significant, though. It means you are not processing speech as well in your AN ear. You hear the sounds, but don't pick up all the details that are needed for distinguishing words.
So, as you said, your hearing is not the best. I agree that having the tests done differently makes it harder to know if that is a change or the same news. (I tried to explain to the audiologist that my tinnitus should serve as adequate masking, but they wouldn't buy that). At least it sounds like Dr. Chang thinks your hearing is stable.
Overall it is a good outcome, and it is good to hear the good news.
Steve