One phrase left in the translation

An original account of an invented translation exercise.

Our class translated a short invented tale into plain modern English. We replaced several old-fashioned words, but one phrase defeated us: the traveller had promised to return before the candle forgot its flame. Nobody agreed on an exact modern equivalent.

We left the phrase in place and added a short note saying that it suggested a brief but uncertain interval. This preserved its strange image without pretending that it gave a precise time. Our first draft had replaced it with in five minutes. That was clearer, but it made a claim the original had not made. We learned that a translation could be easy to read and still be misleading.

In your own words, explain two reasons why the class kept the original phrase with a note.