"Do you mind a little advice? Starfleet captains are like children. They want everything right now and they want it their way. But the secret is to give them only what they need, not what they want."

"Yeah, well, I told the Captain I'd have this analysis done in an hour."

"How long will it really take?"

"An hour!"

"Oh, you didn't tell him how long it would really take, did ya?"

"Well, of course I did."

"Oh, laddie. You've got a lot to learn if you want people to think of you as a miracle worker."

It's a plot point on Lower Decks that lower deckers employ buffer time

From memory alpha:

Buffer time was a means of creatively estimating or exaggerating how long it takes to complete an assignment. A lower decks tradition, it was built on the premise that command level officers had no idea how long it took to complete a task, combining the "you never admit the actual amount of time it takes to finish a job…" so that "you're a hero when it's done early." This allowed the crew time to relax between jobs.

I think it might have B'elanna that tells Janeway that "no, it will take at least this amount of time".

Isn't that the scotty principle.

https://www.urbandictionary.com/define.php?term=Scotty%20Principle