Prose
8. B. U. III. 6
In plain words
This one isn't text to translate at all — it's just a page citation from the printed book ('B. U. III. 6', meaning Bṛhadāraṇyaka Upaniṣad, chapter three, section six), most likely a stray reference marker rather than anything Śaṅkara wrote.
Close to the Sanskrit
This entry is not running Sanskrit text. It is a bare bibliographic citation printed in the source — 'B. U. III. 6', i.e. Bṛhadāraṇyaka Upaniṣad, chapter three, section six — most likely a page or cross-reference marker carried over from the 1910 print edition, not a sentence of Śaṅkara's commentary.