A manuscript catalogue may give more than a title. It can also record the words at the beginning and end of a passage, providing another way to identify what the entry covers.
Read a concrete catalogue example
The British Library record for Cotton MS Domitian A I, folios 2–55 lists several contents and supplies opening and closing wording under incipit and explicit labels. Those details belong to particular entries and folio references, not automatically to the entire physical volume.
Keep the locating information together
Write the shelfmark, folio range, attributed work and relevant opening beside one another. A title shared by more than one work is less useful when detached from those details.
You do not need to translate unfamiliar wording yourself to retain an accurate reference. If you use a translation, identify where it came from rather than presenting a guess as a reading.
Distinguish a passage from a complete work
Check whether the catalogue identifies an excerpt, preface or incomplete section. The first surviving words may not represent the original beginning of a complete composition.
Use folio references to return to the same place. Opening words are a useful additional clue, but they work best inside a documented chain of identification.