CPT® 61516 vs CPT® 61524

According to the code 61516 is supratentorial and 61524 is infratentorial. Our doctor first drilled burr holes then did the occipital crainectory and he went all the way to the pineal region to remove a cyst. Replaced bone flap. I am trying to understand is it the approach that matters or the actual spot you end up in? It does not appear that they are using the burr holes to open up the skull. Maybe more for drainage.

We are being denied for CPT® 61524. Can anyone explain the difference in these two codes?