Prose
S. B. U. II. 8
In plain words
This isn't a line of Sanskrit at all — it's a stray page marker from the printed book's margin, most likely reading something like 'Śaṅkara-Bhāṣya on the Upaniṣad, chapter II, page 8.' It has been left exactly as scanned rather than treated as running text.
Close to the Sanskrit
This record is not Sanskrit prose. It is a page/section citation printed in the margin of the source edition — most likely an abbreviation such as '[Śaṅkara-]B[hāṣya on the] U[panisad], chapter II, page 8' — carried through verbatim from the scanned page. It has been transcribed here exactly as it appears, with a minimal, schema-valid word breakdown rather than a forced Sanskrit reading.