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.